After spending several hours finding a way to make skinning work in OpenBOT version 2.6 I decided it might be a good idea to post the solution here as well.
Could be other users having the same noobish problems like me (didnt really know how to use SVN, open bot dev etc.)
So to simplify as much as possible replace your openbot/objects/oState.iss with the following file (taken from ob-dev.com, HEAD, revision 30):
Changed to direct link: