Reading the blurb for this module excited me. I love urban adventures. In particular, the following line is what made made up my mind on the purchase of Gallery of Evil:
"When the mad painter’s visions come to life, the heroes find themselves entering his crazed landscapes to find a way to stop them from tearing the city apart."
Unfortunately, the adventure doesn't deliver. The heroes go into exactly ONE painting, and the landscape within features a single encounter. A fun encounter, to be sure, but not enough to make good on the blurb's promise.
The storyline leading up to the villain's mansion is very linear. The DM leads the PCs through several encounters by the nose, battering them with "clues" until, finally, their attention is forced to a painting of the villain that they would normally pay no attention to.
The saving grace of Gallery of Evil is the villain's lair at the end of the adventure, and the villain himself. Imron is presented in a unique fashion and, in a way, the heroes get to fight him three times -- a great way to get a party emotional invested in defeating their nemesis without using the old "teleport and fight another day" trick.
Overall a brilliant concept that was implemented poorly. Sorry Mister Greer.