Hi there,
When you're in rommon mode, can you see if you have a IOS image stored on the device?
I think from memory to see what file systems you have you would use the command:
rommon> dev
it should list the bootflash: directory as that is what the 4948's use.
then issue the command
rommon>dir bootflash:
If there's a valid image in there, you can see what the boot variable is using by issuing the command
rommon>set
if the boot variable is not set you can set it by issuing the command.
rommon>BOOT=bootflash:XXXXXXXX.bin
or simply try to boot the image using
rommon>boot bootflash:xxxxxxxxx.bin
If there's no image in bootflash, you need to get one there..
This page should help you in this regard.
http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/release/note/OL_15594.html
Good Luck!
Brad