Projecting Images onto Cyclorama

I don't think Data Projection is going to work well for you. You're right about Projection from the front, It will project onto the performers and cast shadows onto the Cyc (which could look effective!?) If you have sets on stage, you could project onto the top half of the cyc only? In regards to Rear Projection, because the Cyc would be fairly big, you need to have a fair distance between the data projector and the cyc to be able to project over the distance of it. Some Data Projectors allow you to fit a short throw lens to them, but you would still require quite a few metres distance between the projector and the Cyc (and even then, depending on the thickness of your Cyc, a rear projected image may not be that clear). If it is moving images that you are looking for then I do have a suggestion (however is not a cheap one). LED walls allow you to display images on them from Data or Video. Do a google search of them and you will see what I mean. Contact an AV company in your city and they will be able to provide you with dimensions and hire cost. These are used in a lot of live concerts and add a very bright and effective visual to the stage. It would definately add a modern edge and a different dimension to a ballet concert! Good Luck!