I agree, and use Gimp myself for the majority of tileset work. (Gimp can be downloaded for free online somewhere. Google it)

Also, for creating images based off standard Jazz sprites, you should look into NeoBeo's sprite dynamite (Downloadable from J2O.)

Is the still image you see at the end of an episode that you are refering to the picture for the next episode that you see when choosing an episode? If you want to make these, there are also a couple of .j2e creators you can download from J2O to create these.