Ashrem's room contains a collection of monster heads that he and his party defeated.  

Ashrem collector of heads.

Osyluth Head Killed with Lysander after separating from the party
Osyluth Tail After being stung, Lysander and Ashrem managed to kill this evil devil.
Mind Flayer Head Ashrem damaged this vile entity and was wounded badly.  The wounds made Ashrem revert to rat form because he was a were-rat at the time.  He then proceeded to bite this Illithid to death.
Medusa Head Ashrem took no part in defeating this Medusa, since he became a rat.

In memory of his party he severed the head after all the combat was over.  Lysander was turned to stone once the medusa gazed upon him.

Orc Mask Ashrem killed a sentry and used his face as a mask to sneak by some guards.
Grimlock Head Outside an abandoned warehouse, Ashrem and his party defeated this Assassin Grimlock and her followers.
Black Dragon Head Almost sacrificing his life for the party, Ashrem waded out into a dark pool to lure the dragon out.  The party quickly dispatched the young dragon.  Ashrem took hours cutting the head off.
Bear Skin In a dungeon, Ashrem single-handedly defeated a bear while the party defeated its keeper.
Unicorn horn Not killed by Ashrem, but kept as a token because it helped Ashrem wound a Vrock.
Tiefling head and tail pictures not available In a temple in town we encountered this tiefling and defeated it.
Were-rat heads resort back to their previous race
Ogre Mage disappeared once defeated.
Red Flesh Golem head It attacked us in a tower of evil
Hobyah head Those little critters were mean, we found plenty in the forest around this small village.
Girallon head and 2 arms. These monkeys were bad, they tore one of our party in half.
Desmoduo head We found some bat-like men, then killed them.
Broken Beholder parts and a Beholder carcus These guys were a nightmare.
Vrock head Not the Lydia released, but another
Half-dragon/Half-orc He wasn't too friendly
Effretti head He bull rushed me into a pit of lava, we showed him.
Salamander head Magnarus banished him, he came back the next day, so now I have his head on my wall.  He nearly killed us all.