What can I check, other than the fuse pannel, to determine the source of my reverse lights not turning on when I back up? I've checked the bulbs and the fuse, all good there.

 

The bulbs within your lights themselves, perhaps?

 

They are switched on thru the transmission selector switch in reverse.
No relay involved.
Check for voltage at the lamps. If there, the bulbs are either blown or there is a bad ground.
If voltage at the output side of the fuse, the tr switch is suspect. Or a break in wireing.

Fuse--selector switch-----lamps-----ground.