Do you have free file upload or email or something?
I have made a small change on yumi giving it a clean wooden texture like the tartar. The yumi has two textures actually, so I copied two different ones into them and you can just barely see where they don't match in 1st person, however I think that's intentionally so (laminated bow?). It also has doesn't have those cord thingies, that would be too much work.
(edit: If you want to it yourself the files you need to edit are C:\Program Files\Mount&Blade Warband\Modules\cRPG\Textures\bows_2048_heir.dds and the _norm and _spec versions. You have to copy for each version exactly the same areas into the two yumi areas which are in the middle directly left of the quivers. You'll need photoshop or gimp and a dds plugin for that and save as DXT3 8bpp with explicit alpha and no mipmaps.)