Go for it. Faux finishes on textured walls are wonderful. Do you know what kind of finish is on the walls now? Flat, eggshell, etc.? You can do the technique I describe on any sheen, but it is a little harder on flat. If you use a dark colour over white there will be high contrast. So you might want to try the technique on a sample board first. Just base a poster board in your wall colour, let dry and then do technique in a few colors. Choose the one you like best. Colors close in tone look soft and subtle.
I would suggest doing an easy colorwash technique. You can dilute any color latex paint with water in a ratio of 1 part paint to 3-4 parts water. I prefer to use an old washcloth, but you can use a sponge. Dip it in the diluted paint, wring out excess, and start wiping on walls in circular motions. Use the same motion as you would washing the walls. Start at the top and work down. Re-load your rag or sponge often.
This goes really fast and you can repeat it several times to build up depth. Just let each coat dry first. Good luck and happy painting.