Icons too big?
 

I have recently switched to DarqUI. I have some problems and suggestions (will do them later) but there is a bit annoying one for me. Many merchant items are kinda seems buggy to me as seen in the picture. Is there a way that I can decrease icon/font size of those?

Standard DarqUI doesn't modify the Merchant window, so you are seeing the default font and icon sizes. They can be reduced, but there is not a convenient setting to do so. A copy of the window would need to be modified.