I would Recommend just Deleting your current mmCM Installation & Re-Installing the Latest Version of multiMAN MOD first, Then we can try to Fix your Covers & BIN's & CUE's. (BIN/CUE is Recommended!)
Copy out any Files you want to keep from your mmCM Install under: /dev_hdd0/game/BLES80608/
Then Highlight MutliMan from the PS3's XMB & Delete. Install Newest multiMAN MOD via Package Installer.
Assure your Images are Named correctly, Which for PS1/PSX & PS2 Games will be as the following Naming Structure w/ Uppercase File Extensions: SLUS_xxx.xx_COV.JPG or .PNG
^^^ Where SLUS_xxx.xx is Replaced with your Games' Title ID, Just make sure not to forget the Underscore & Period inbetween the 3 & 2 Characters after the Region Correspondence. (For Europe it will be SLES rather than SLUS!)
Example using the Game you Requested/Provided: SLES_010.42_COV.JPG or .PNG
Put your Cover Art Images under: /dev_hdd0/game/BLES80608/USRDIR/covers_retro/psx/
Alright, Now for the Game Roms themselves. You're going to want to keep the BIN's & CUE's inside a Folder. As long as you place your Games within the Directory that multiMAN will be Searching for they will be found, Which is under: /dev_hdd0/PSXISO/
When Applicable, Games' Folders & Roms themselves can be Named with any Naming Style you choose, As long as the BIN/CUE Files both have the exact same Name as Each other as well as the Folder they are Contained in. For Example once again using the PlayStation 1 Title you have Selected;
BIN/CUE Extension Example: /dev_hdd0/PSXISO/Actua Golf 3 (PAL)/Actua Golf 3 (PAL).BIN + /dev_hdd0/PSXISO/Actua Golf 3 (PAL)/Actua Golf 3 (PAL).CUE
If you are still having problems, Just remember before you attempt any of this the Covers themselves need to be Resized to 240px x 240px to Ensure Compatibility.
Hopefully you can Figure this all out & All the best!