MG Mods
Game sounds can be changed, and the animated reel symbols are stored in separate files, but the general reel bands are in DAT files, and are coded, so this would count as code modification rather than image and sound replacement. Also, if the casino asks for a screenshot as proof of a big win in dispute you're screwed if you have changed the images. Casinos can 'mod' the pictures and sounds on the games. Look at 'Double Magic' slot in any BelleRock casino and note the blue star is replaced by the BelleRock logo.
You can also modify some parameters in the later Video Slots that are no longer available in the expert interface, such as 'stop when lost x credits', and can remove the compulsory delay between spins in Secret Admirer - useful if offered in a wager challenge tournament.
I have even designed a registry merge file to swap all my Casino software over to 'tournament' mode and back to 'normal' once the hour is up! This saves around 5 minutes, significant in an hour long tournament where the server runs at a snails pace and can often crash with MG 'casino eror 2'.
I am certain the flash movie can be killed off, although I have not seen a specific registry parameter that does it, so it is most likely in one of the INI files as mentioned previously. I have had MG crash on start up too, but rebooting my PC clears this. I suspect repeated use of the casino leaves 'garbage' behind which eventually kills Windows.