Glossary
bcache*.bmc
The legacy RDP bitmap cache files bcache2, bcache22 and bcache24.bmc: fixed-size slots of 8, 16 or 32 bpp tiles, some compressed with interleaved RLE.
bcache2.bmc (8 bits per pixel), bcache22.bmc (16 bpp) and bcache24.bmc (32 bpp) are the legacy RDP bitmap cache files; bmc-tools also mentions bcache23.bmc. They were written by older clients and can still be found on current systems.
As reverse-engineered by bmc-tools, the files have no header: they are a run of fixed-size slots, each a 20-byte header (two key halves, width, height, data length, flags) and a 64×64 pixel area. Rows are bottom-up, flag 0x08 marks a compressed tile, and reused slots can keep slot remnants. Details: the bcache*.bmc and Cache*.bin file format.