one idea i had was putting some paper birds on a string and having a motor move the string.
That reminds me of something they were doing in the "psychedelic 60's"... They would take a speaker and stretch a rubber membrane over it. Then they would glue little front-surface mirrors to the membrane, and dangle mirrors from threads so that they would just-touch the membrane. Then, shine colored lights on it and "project" against a screen or wall. I never saw this in real life... I just saw pictures...
Even if you don't plan on buying anything, you should probably take a look at what's available commercially, to get some ideas. Chauvet Lighting
is a good place to start. Just be aware that most of the pictures and videos have fog or haze, and without it you won't see the light-beam... You'll just see the colors hitting the people and the walls.
I've built a couple of lighting effects, and I'm working on a new one... Maybe they will spark some ideas for you.1.
My "main effect" is 4 colored spotlights (actually 4 pair). It's triggered by the beat of the music, and every time it detects a beat it pops-up a random pattern and holds 'till the next beat. It's simple, but the randomness keeps it from becomming too boring. The beat detection isn't perfect, but I suppose that adds to the randomness. This was built without a microcontroller.2.
A 4-channel chase-light controller. My original idea was to hook-up 8 christmas-light strings in a big "star" over the dance floor, so the whole ceiling would "rotate". I still think that's a cool idea, but it wasn't very portable... It takes "forever" to hook-up the lights, and if you have to find a burned-out bulb... So now, it's running a "rope light". A bit more "traditional", but a lot easier to set-up. I'm thinking of something new... I'm thinking about 12 ~30W floods in a row on a 10 - 12 foot piece of ABS pipe...
Now the "cool stuff" about the chase-light controller... The speed is controlled by the loudness, and the direction is triggered by the beat. But, there's a delay so it doesn't change direction on every beat. This one doesn't use a microcontroller either, but it automatically adjusts to the average music level, so there are no knobs to mess with.
Of course it does the traditonal chase pattern, which looks like this -
You generate that pattern by looping the output from channel 4 back to channel 1. But, if you invert channel 4 before feeding it back into channel 1, you get a more interesting Johnson Counter
, which looks like this -
Of course, 1 is on, and 0 is off. I hope that's not too hard to visulaize...
Now, there are 4 modes... I can loop in both directions, loop in one direction and Johnson in the other, or Johnson in both directions. If you randomly switch modes at random times, you get even more patterns, because you can start the regular loop-chase with 1, 2, or 3 lights on, or with the Johnson counter in a "funny" pattern, and things get interesting and fun to watch.3.
My current Arduino project started-out as a giant 8-foot tall bar-graph VU meter. (It wasn't going to need a microcontroller.) Then, I started thinking I wanted a chase-like effect, and i realized if I used a microcontroller it would be easier, and I could add a "Knight-Rider" effect, and toggling on & off, and running everything including the VU meter in both directions, or I can make the left-channel meter go-up and the right-channel meter-go down... and I've got ideas for about 10 different modes with variations of each mode... All selected automatically/randomly. The 1st version is 7 channels to run some short 14-light rope lights. The hardware is mostly done. I've got everything in a box with 7 "test/monitor" LEDs and 7 solid-state relays, and an audio peak-detector circuit. The software is still in the experimental/development stage. The 2nd version is going to be the 20-channel 8-foot version.