I recently had a customer contact me because the decal they installed was starting to pull away from the wall. I thought this was strange because we use the best vinyl available and have never had a customer have that problem before. I soon found out that they had applied their decal to a textured wall. Ahhhh... now I understand! While we do not recommend purchasing wall decals for textured walls, it isn't impossible. In fact, I have textured walls in my own home that I have applied decals to. I feel your pain!
The best way to insure that your decal stays on the wall for the long haul is to simply heat up the decal with a hair dryer while you apply it. Warm it up and REALLY rub it into the wall. What this does is re-form the vinyl to the textures in the wall. That's it! Just remember to take your time.