If you don't like a certain icon (or all) then you can just replace the exising ones, they're plain normal files inside
share/CodeBlocks/images. You may have to make sure you get the sizes right, for some of them have hardcoded sizes if I remember correctly.
Generally, being able to easily theme icons is of course a nice gadget, but you'll understand that as long as we still have real bugs and real IDE issues, this is the absolutely least important thing
EDIT: Hmm wait a second... in case you're talking about the Explorer icons, that's a different thing of course. Those are not quite so easy to replace. On the other hand, this would be rather easy to implement, once we've settled on the final numbering scheme.