I think the issue is the color palette with 256-color mode. Even if your plug-in bitmap looks fine by itself, it becomes ugly with other plug-ins because the color palette must be adjusted with other bitmaps. For this reason, I would recommend you not adding 256-color bitmaps. Just use true-color bitmaps and 16-color bitmaps, and omit 256-color bitmaps. In most of my standard plug-ins, I don’t supply 256-color bitmaps any more for this reason. Most PCs now display true color, and 256-color mode is becoming obsolete. The 256-color mode feature might be taken out in the future.