Posted 15 May 2014 - 08:57 AM
i can recommend the free programs blender and sketchup for 3d modelling but what you are discussing appears to be texture mapping. if you are editing existing models they model will be saved as a .obj/.3ds/.dae/.fbx/.max/.blend/.skp/other within a folder and somewhere, perhaps in a sub directory of that folder, will be the texture images (as.jpeg/.tga/.png/..gif/.dds/.bmp/other). these texture images can be opened and altered with paint or gimp or any other photoediting application. then save the edited textures over the old ones(back those old ones up elsewhere first) with the same names in the same folder. now open the model with blender(blender will open blend files and can successfully import 3ds/obj/dae and a few other formats, other importers can be found online as scripts for it) and render it to see how it looks with the new textures, lights can be added so you can try different lighting setups. then repeat the process of editing the texture image and saving it over the previous one (same name in same folder) and checking out the changes in blender until you are satisfied. your explanation is very unclear so i assumed you were talking about texture editing on existing models, texture mapping is harder as you have to tell the blender what part of the image goes onto each face of the model. for games your finished blender model might need exporting to a weird format, depending on the game, which might require exporting via a series of formats before you can reach the one you need. blender will let you easily import many objects and position them to make map like environments.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB