Unless I am mistaken, I believe he was just asking for the programs that are generally used when players mod Legions. For modding, go with Photoshop (better, but $) or Gimp (still works fine, free) , and paint (free). You must also get the .dds plugin for photoshop or gimp respectively. Gimp and paint are all I'm using at the moment, and its all I need.
However, if you are interested in modeling, the best programs are the ones you have to pay for, Maya, 3D Max, etc. However, I currently have 3 free programs: Blender, Google Sketchup, and Milkshape 3D. While I never really use them because I have never put any really effort into modelling things, I believe any of these three can get the job done. Don't buy things just so you can mod/model a game.