Dungeondraft is a rather nice tool for drawing RPG maps. It's designed for small scale tactical maps rather than world maps. It also has an option to bring in custom assets.

Given the predominance of Fantasy assets for Dungeondraft, I've decided to try and do my own asset sets for science fiction, principally focused around Traveller. There are three asset sets at the moment, focused on Starship deck plans, starports and trade goods.

• Starships
• Starports
• Trade

All are available for free, along with the SVG and XCF files used to build the assets.