GIMP + GAP (GIMP Animation Package) can provide you the needed tools. You can even configure GIMP dialogs and toolbar to look pretty much like Pixen GIMP has a good set of tools for pixel art and work with indexed palettes.
To the rest: Although it is true that Ubuntu isn't 100%, I don't think this thread is the place to discuss such thing. It sounds more friendly to suggest a 100% libre distro rather than bashing people because they don't use one. In that case, I'd say that Trisquel is a good recommendation, since, being an Ubuntu derivative, it provides the majority of the "user friendly" features with 100% free packages. For a user who doesn't need 3D acceleration and can live with a partial Flash support, it's probably the best 100% free gnu/linux distro out there for newcomers. 2011/9/6 C. A. MacFinn <c...@cgmuse.com>: > I am working for a graphics company that needs an application that will make > sprite sheets and animated gifs. We have been using Pixen on the Mac but are > switching many of our workstations to Linux. Is there anything equivalent to > Pixen that runs well on Ubuntu? > > Thanks, > > C. A. MacFinn >