You need lava lamps in triads. One, or even two, is just not enough. You need the "pyramid of power"! Just remember, when you are doing vocals to have some extras for the singer (the bastard will take yours!).
How about just getting a set or two of X-mas tree lights and stringing them around the room just below the ceiling? zYou can get different colors or all blue or all white... Just don't get the flashing ones - too distracting.
You'd be MUCH better off getting rope lights. They're LED's so you don't have the problem of them going out every single time you touch them. You can actually buy rope light in any length you want. You can buy it on a 1,000 foot roll if you'd like and cut it to the size you want.
That's actually a good suggestion for brigning ambience to a room. We used this technique where I work when we remodeled our conference room.