PS1/2 Artwork not showing up in OPL

[OldGnashburg]

I can't get artwork to show up in OPL. I downloaded two different archives of art, and placed them in the ART folder in my OPL partition, but still nothing. Is it an issue with later versions of OPL, (I'm using the latest nightly 1850 I believe)? Is it because I have a fairly large OPL partition? Is it because after I install new PS2 discs I rename them and remove the SLUS/SCUS prefix? Could anybody help me out?