Yesterday I was working with Arno of FSDeveloper.com fame, and he showed me Gimp, the free program he uses for painting his FSX models. Since I got another question about painting today, I thought to do a quick search and see what else is there, besides Gimp.
The sheer cost of all the modern tools is certainly a problem for freeware developers AND some payware designers alike. So Gimp can be downloaded here and Paint.net is another nice – and free – tool that you can find here.
Personally I continue to use the tools I got used to, i.e. ACDSee Pro for the initial work on my photos, Fireworks to work with graphics in layers and SkeychUp Pro (or GMax when needed) to do the modeling.
Of course there are many other tools around (notably Paint Shop Pro, Photoshop, 3DSMax to name but a few) and ultimately every person will find his own preferred set of tools to work with.