One GM ran an entire Midian campaign based on magical objects of art. Some of these include:
Rune stones: These looked like Futhark-style divination casting-stones, but using an odd alphabet, and with uneven sides. These were part of a magical inscription on a tablet that was broken and scattered to end the spell. When assembled, the magic spell wa reactivated (I don't recall what he said it did, though).
Gateway paintings: These landscapes were actually portals to the lands that they depicted. Most of these were portals to unfriendly dimensions. As the size of the gateway was limited by the picture's frame, and the trip was one-way, they had only very limited usefulness as transportation devices.
Summoning paintings: These portraits of Demons had summoning circles hidden within. Under the right set of circumstances--typically a command word, but sometimes just looking at it too long--the Demon depicted would be summoned. As there was no protective circle for the unknowing summoner to stand, anyone nearby was at the mercy of the creature. These were created by the same artist that made the gateway paintings.
Quick cup: A failed attempt at mass-producing magical potions, this was a cup that, despite being magical, didn't really do anything useful. The player inscribed the cup with the Wayfarer spell (increases speed and lowers reaction time) using Lunaruen (mystical language that allows you to set a spell on an object, the spell becomes permanent). The intent was to make anything put into the cup become a Wayfarer potion, but the magic affected the cup itself. While the cup was permanently quickened, cups don't really do much--they just sit there.
Cruel daggers: There wasn't an overt special effect of these daggers. They were each bejewelled and inlaid with precious metals and other valuable materials. However, the gemstones contained the trapped souls of those that angered the necromancer who commissioned them. This way, the daggers acted as both gift and threat--the message being "I can provide nice things for you, but if you cross me..."
Jade throne: Carved from a huge single piece of jade, this throne was another failed magic item. It was meant to give the warlord who commissioned it the ability to control all Orcks in Midian, as well as allow him to project himself to distant lands. The jade throne didn't provide the total control that the warlord wanted, instead it just gave some Orcks an increased feeling of unease. However, since to a typical Orck, that hightened their aggression, the warlord still got the increased worldwide violence he wanted, just not with any strategic control. The projection power was a form of astral travel, and the warlord forgot that it didn't physically move his body when the Orcks rose up against him. As his consciousness was elsewhere, he was an easy target for their revenge. The throne has since been broken up into smaller pieces by invading mercenaries unaware of its magical nature.
I'm sure that he had more, but these are the ones I remember him telling me about.