A bunch of people on here can't fathom not going to CCC and/or driftorzing the streets when it rains. Do your thing, man. There's no reason you can't put 20's on a 94 Altima. After you find the right wheels, the tire is really what makes it work. Here's a suggestion....

The stock 94 altima tire is 24.7" tall (across). A few manufacturers make a 225/30R20 tire, which would be 25.2" tall. That's pretty damn close. That would give you about 1/4" of lift from the tire being bigger. The General Eclaim UHP is $131 in this size at TireRack. This is probably the setup that the white car above has. You should be able to do this easily without cutting or lifting.

That's only 2.5" of tire though, and I'm not sure trust my wife driving around on something like that. You can also do a 225/35R20 that's 26.2" tall. This will give you about 3" of tire and 3/4" lift. If you want that lifted look, this is what to get. It'll also really fill in those wheel wells once you put about 1.5" of drop on it. Kumho Ecsta SPT's are $129 a piece in this size at TireRack. This might actually not fit, so take your stock tires and measure out 3/4" in all directions and see if it will hit anything.