what the heck is it with these replies
u can create folders all you want on external hard disks that are used on time machine, regardless if its an external hard drive or if its an actual timecapule
you dont need to make a new partition or erase it.
i do this all the time i got a bunch of tv shows on my time capsule router and i sometimes will put photo and itunes libraries on my external hard disk that i use for time machine
just don't touch the backup directory or put anything in the sparse bundle file
aside from your hard drive crashing, which is true of all hard disks, the only bad thing about putting tv shows and other files on your time machine drive, is your video playback may suffer if your doing a backup at the same time your watching nat geo
regardless if you put files on the same disk or on a different partition, you will have less space for rolling backups and older content will delete itself from your backup quicker once you run low on space.
the only time you need to make separate partitions for time machine is if your using the same hard disk to back up more then one computer ( connected directly using usb) . i dunno if its true. but thats what i tell people to do