Just so you know, you do not need a separate service for each raster.
Sure, if you want to pull each one in as an individual layer. However, you could put all of your rasters in a single map document and publish. then just add the REST endpoint to that service and you will see all the rasters with a checkmark in front of them to turn on/off in the FV app.
Just depends on what your final outcome/useage is.
R_