Though sadly not as complete as the Keen 4 set, I have recently been compiling a few misc Keen 6 sprite patches. Most will not be found useful by people here, and there are many missing, but there are some useful things as well, and i hope to constantly update what I have to add more.
The current sprite patches are located here: http://levellord.toxicsheep.com/Index/K ... 20Patches/ if you're working on Keen 6 sometime, you may want to give them a squizz.