Acoustic Plaster is most of the times used to create a seamless acoustic ceiling or wall. So the thought of projecting images on such a surface is not far fetched. If you want to do so, there are a few thing you need to consider:
Acoustic plaster is constructed to be acoustically transparent. This means that it is quite porous in its composition. On smooth textures like Fellert Even Better Silk, these pores are invisible to the human eye, but on other types of acoustic plaster they can be larger and that might distort the image you are projecting. Distortion can also appear if the texture of the acoustic plaster is not smooth enough, regardless of the pore size. Imaging projecting images on old time popcorn textures. That will not be very appealing.
Acoustic plaster often comes with limitations on how large areas you can plaster without having to add a control joint. On some products like Fellert Even Better and Styjl Straight Up, you can install very large surfaces without control joints (>500 m2), but on some other systems you need to add a control joint every 10 meters or if you exceed 150 m2. This is important to know because if you are projecting your images on a control joint, you will experience substantial distortion for sure,.
Acoustic plaster is many times sprayed on an absorbing core, like fiberglass, perforated drywall etc. The joints between the boards of this absorbing core is playing a critical role in the final appearance. Joints telegraphing through in your seamless acoustic ceiling is not on your agenda. And even if they are not visible under normal conditions, they might appear when the strong projector might hits the surface. A good advice is to take a close look on how the joints are treated in the system you are about to get installed. If the joints are filled with joint filler, mud, tape etc. you should proceed with care. It is a substantial risk that you will experience telegraphing joints. Especially a few years after the installation was done!
Here is an example of an installation where movies are projected on the acoustic plaster. Link to Maui Ocean Center