Code is not universal and neither are resources, some rely on 46611, others rely on 1112, rare ones rely on 592.
Window and taskbar icons rely on BMP's and ICO's. So you will have to change each one accordingly to make it work. The best method is to simply look over all of messengers resources and edit every single one that you see a buddy in.
Skinning was never easy, and this is one of the reasons why.
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