If you want a reasonably fast image editor that doesn't need internet access and you don't mind running a debian chroot (easy debian), I can recommend "mtpaint".

It doesn't use many resources and its quite fast at loading pictures and making changes to them.

The only downside is that it dosn't have a not a native Maemo 5 port, so you have to use the stylus all the time. Perhaps someone should consider porting it?