This has actually come up in my game. Initially I just handled it as a Trade (eg 100cr a month). It's easy and won't really impact your game either way, but I thought it lacked a certain fun about the wild and wacky world of art.
So I made the system below. The gist of it is to handle art as kind of speculative cargo. The system below seems complicated, but it's actually not. Try running it a few times and you'll see it doesn't really slow down the game.
There's basically two avenues for people who are good at art to make money, what I'll refer to as a "employee" and "free creator." These divisions are not indicative of how artists in real life should be treated; just how they could be treated in-game.
An employee is just that, these artists are in the employ of someone else and create works that their employer asks of them. Regardless of their origin, they are commissioned to create something for their employers under some sort of contract. While most of employees have little reason to travel, it's not hard at all to come up with a reason. These are obviously best modeled using the Entertainer career.
A free creator is someone who doesn't have an employer/patron. I think this is what most people think of when they think of artists. In fact, this freedom is very important to them; they want to just create without any rules. This means that the overwhelming majority of them struggle for money and most have other jobs to make ends meet. In RPGs, this isn't a bad thing: The artist probably has some sort main job as a member of the crew and just does art as something on the side. The system below is oriented towards free creators.
Step 1: Determine the multiplier value of the art. This represents an abstract value on how "good" the artist's skill is in comparison to other artists. Remember, art is in the eye of the beholder; while most of us can say one person's guitar playing is better than another's, who knows what certain quality an artist has to be able to take cardboard he found on the street, mount it on the wall and it gets valued for hundreds of thousands of dollars/euro/whatever - for this it doesn't matter. It's just that the artist has whatever quality or not. The base value is determined by the art skill in question to determine the multiplier of the art in terms of hundreds, thousands, and so on. The base multiplier is 1Cr for Art-0. Each actual level adds an additional tens place. So a character with Art-0 creates art with a 1Cr multiplier, Art-1 is 10Cr, Art-2 is 100Cr, Art-3 is 1000Cr, etc. Yes, by the time you're at at Art-3 you could probably be doing that full-time instead of Travelling. Yes, the modifier at Art-4 and above becomes pretty intense but seriously, if someone is that much of a prodigy they're either min/maxing or they should likely have some good reason why they're Travelling instead of just doing art as their life.
Step 2: Determine the Market. Use the Destination World for Passengers on the Trade Table as die modifiers (you can ignore Red and Amber Zone modifiers). Wealthy, high-population worlds will have more people interested in diversions such as art as well as the money to spend on it. Similarly, poor, low-population worlds will have smaller economies, and even if the people are interested, they're likely to have more pressing matters than spending money on art items.
Step 3: Determine fame. In the art world, your fame as an artist is everything. Even if you're a talented unknown, your stuff likely will sell (earn) far less than a famous artist who has marketed herself well. By default, I think most Traveller artists are basically the equivalent of a street artist; that guy strumming a guitar in a shopping mall or downtown, the person selling crafts at the art and wine festival, and so on or in Traveller terms, a sculptor selling items at the local Startown rent-space-by-the-day section, a musician playing at the local startown bar, or someone holding plays in the streets of the startown. It's assumed in this system that the artist is a total unknown and so suffer a basic penalty of -5.
Step 4: Determine Promotion. How well you sell yourself (and your work) is very important and is based on Promotion skill and as an artist IRL, I can tell you it's pretty much as important as how good you actually are with whatever art you do. Promotion opens the door, your skill in art determines if you stay or not. A character with the Entertainer Career may use half of their Carouse skill (rounding down) as a modifier. Those who aren't in the Entertainer are counted as simply not being very good at the kind of self-promotion necessary. Otherwise, they may hire a promoter who works like a broker in the Trade system. Unlike brokers for trade, a promoter takes their Broker Skill x 10% of the profits (so a Broker +1 takes 10%, a Broker +6 takes 60%). Promoters aren't stupid; they won't promote someone without that certain something; a Promoter's skill may never be higher than the Art skill of the artist they're promoting. Self-promoting and hiring a Promoter in this are mutually exclusive: You either use half of your carouse (as an entertainer), hire a promoter, or go without. Promoting and Broker are actually separate skills: Your trade broker buddy can't promote you.
Step 5: Market your product. The price is: 3d6 + (Market Modifier) + (Fame Modifier) + (Promotion Modifier). Then you compare the total to the Modified Price Table in the trade section. This is how much your art pulls in. I say that a -1 or less result is automatically 0Cr pulled in (nobody likes your art). While having its own table would probably generate better results, I like being able to reuse resources. Unlike trade, you must accept this result. You may only make this roll once per month on a given world, just for the sake of balance.
Optional Step 6: Fame? That 3d6 roll from above? Take that 3d6 and add your Art skill to it. If the total is 18 or higher, for whatever reason, the locals take to your art. You gain a point of fame on that world (offsetting the -5).
Obviously, an artist who has a high art skill and starts acquiring fame on a world may wonder why he or she is still Travelling. I don't think this is ridiculous; it happens in real life too.
