What would a consumerist culture be like in a fantasy world?

I think you first need to determine everyone's quality of living. Since everyone has a passing knowledge of magic, does everyone in this society already have their basic needs easily met (e.g. food, shelter, clothing)? If not--and this is the case for most fantasy worlds--there's probably not much of a consumer culture at all. Most pre-industrial worlds are a barter and trade society, and if there's a form of serfdom, there's also taxes to pay. The average person would work their butt off to grow enough potatoes (or whatever) so that after paying 60% to their lord, they'd have enough to trade for other necessities.

Assuming you have all that stuff accounted for and people are pretty well-off in your world, here's some suggestions for consumer goods that might be popular: artwork (everything from paintings to sculptures to pottery), coaches (or chariots or horses or airships or whatever mode of transportation there is in your world), fancy houses, servants... To be any more specific than that, I'd think we'd need to know your world better, because ultimately the consumer culture needs to be organic with the world you've imagined.

It depends on the magic.
If it can be used to spy on people, they might do that... watching the "savages" halfway across the world might be interesting. If it can be used for some kind of games, or competition I'd imagine there would be a lot of that.
Creating music and art and food that might not otherwise be possible. Doing stuff with animals, like possessing them and making them fight (yeah. rich people can be dicks) or do tricks or whatever. It really depends on what kind of magic you have.

You might want to look up what decadent royalty in the past (I'm thinking specifically of royalty in old-time China and France but they were just the first to spring to mind) used to do to get their kicks.

- Illusions (would include makeup, tattoos, incorporation into clothing and jewelry similar to holograms, interior decorating, sculpture and paintings, possibly movies)
- Bodily modification (plastic surgery would be a big recreational if it were more painless and safe)
- Recreational drugs (aphrodisiacs, temporary transformation into an animal, psychedelics and euphorics, temporary bodily modification such as simulation of a pregnant belly, triggering of lactation, temporarily huge genitals or breasts, anything that appeals to any sexual kink really)
- Magical pets, magically tweaked working animals, and flashy transportation (horses with fake wings or rainbow colors, golem horses that don't go lame and don't need to be fed and won't crap all over the place, tame tigers and dragons, hovering boats or flying carpets, personal submarines)

Hey, if you can conjure objects at will, all material wealth becomes worthless and you slide into Post-Scarcity territory. Consumerism as we understand it breaks apart there.

I'm thinking something like Dancers at the end of Time here, or Drinking Sapphire Wine.

Think big, think weird. The more money (magic) people have, the weirder they seem to get. Richard Branson is building a space ship. Larry Ellison flies himself around in his personal military fighter jet. Why? Because they can.

Depending on how the magic works, they might have an array of convenient little enchanted objects that supposedly make life easier, but really function as status symbols. *coughiPadcough*

alcohol.. alcohol.. and more alcohol.