Some popular RocketDock icon packs include:
A RocketDock icon pack is essentially a collection of .png images bundled together, designed specifically to replace the default shortcuts in the dock. Unlike standard Windows icons (which are often low-resolution .ico files), RocketDock icons are typically high-resolution PNGs with transparent backgrounds. RocketDock Icon Pack
While less active today, IconArchive remains a library of millions of free PNGs. Some popular RocketDock icon packs include: A RocketDock