After upgrading my OmniGraffle Wireframe Palette a few months ago, I noticed it loading really slowly. Upon inspection, I found that it was abnormally large and subsequently found the icons to be the culprits. I finally got around to modifying the icons in Illustrator and exported them as PNGs with transparency. Filesize was reduced from 2MB to 800KB. I do not have the time to organize the icons in the same way as the original but it is close enough.

>> Download OmniGraffle Wireframe Palette (modified)