For tokens, there is a great online token creator that I use for my VTT tokens. You just drop in your image, customize it with given options and it's done. Here's the address: https://rolladvantage.com/tokenstamp/
For maps, I just do google image searches. There are a ton of maps for VTTs already floating around. However, I mostly do theater of mind and use maps only as a last resort and/or for complex battles. For the most part I only use mood setting background images. It's a matter of play style, of course, but I've found that having a map easily locks players into "boardgame mode", where they act like they are moving pieces on a board, which IMHO detracts from the roleplaying experience. YMMV, naturally.
If you really want to draw your own maps, there are several dungeon mappers online which can be used for sci-fi as well. They are bare-bones, but have served me well enough. Just google e.g."dungeon mapper" and you'll find several. I generally don't want to spend hours doing maps, I like to use that time prepping the game in other ways. And as my players do not expect eye candy from battle maps (thankfully), those simple dungeon mappers are what I use if I need a battle map if I don't find a suitable ready-made one from the Net.
PS. The character sheets for Traveller on Roll20 are in dire need re-doing, they are quite primitive. They will do in a pinch, sure, but it would be glorious if someone would re-work them into something more modern and easier on the eyes. I have no coding skills, so I can't do it, sadly.
