Yeah this is definitely something that's actually been on my list for 2.0.
The current UI isn't set up for it, but a revamp of the interface could take into account a wider range of features, including brushes. REXPaint was initially envisioned purely as a cell-wise editor since that was all I needed for my purposes (it being an in-house tool for my own projects
![Tongue :P](http://www.gridsagegames.com/forums/Smileys/default/tongue.gif)
), though I've since been adding what I can to support other types of users where possible.
Unfortunately certain other features like this need to wait until I can organize the next phase and work them into a cohesive UI. (Note there are other ASCII editors that do brushes, but overall not as usable as REXPaint in general...) Your idea with the brush-type texture areas is definitely something people do, either putting them in a separate image you can flip back and forth between (Ctrl-Tab), or in a separate layer of your current image, or somewhat outside the bounds of your current image and you just cut that out later.