has updated CXMB today, a Custom Firmware plug-in that allows users to install custom made XMB themes from the memory stick rather than by copying files to the PSP's flash memory.
Now compatible with 3.71 and 3.90 M33 series Firmware, the plug-in introduces a file format called CTF (short for CXMB theme file).
Download: CXMB for 3.90 M33 with Theme Creator
/ CXMB for 3.90 M33
/ CXMB for 3.71 M33
When installing a new theme to the memory stick, CXMB automatically creates a Default.ctf file on bootup which contains the contents of the installed theme.
Finally, pre-made themes in CTF format are available from the author's site HERE