High-quality archives use suffixes (e.g., [RMGE01] for NTSC-U Super Mario Galaxy ). This helps loaders fetch cover art and game metadata from databases like GameTDB.
Historically, Wii games were ripped from physical discs into raw .iso files. However, modern preservationists and players heavily rely on WBFS archives instead of standard ISOs. ISO vs. WBFS: Why Format Choice Matters