I recently got the 10-game Taito bartop version. It's quite nice.
Like others in this thread, I'd like to see if it's possible to make changes to the disk image (to remove the distracting background in Space Invaders, for example.) After some tinkering with that master.img file, it appears that it is really a simple zip file (just copy it and rename the copy to master.zip, and attempt to unzip it.) However, it's a password protected zip file.
You can at least find out the filenames this way (for example, .rom files for the games, and the .bmp file for Space Invaders that I'm itching to get at.) No idea how to proceed beyond this, however.