Your vinyl decals should remove easily without causing any damage. First use a fingernail or other small edge to loosen a corner of your sticker. Then slowly begin peeling the vinyl at an angle.  Instead of pulling straight out from the wall, keep your hand close to the wall and pull at a downward angle. Continue pulling slowly until the entire design has been removed.

Troubleshooting tips:
If you do notice any paint beginning to pull away from the wall, stop and try these tips.

You may need to use a blow dryer to warm the vinyl before peeling. This will loosen the design and make it peel off more easily.

Another option is to simply try pulling the vinyl from a different direction. Often this is enough to stop any paint from peeling.

As a last resort, you can try using a liquid vinyl removal spray.  This is very rare and shouldn't be needed except in very special cases. If you do use something of this nature, be sure to read and follow the instructions.  Letting the liquid sit on the vinyl for the proper amount of time can make a big difference.