Can you tell me if a child can suffer from retinal hemorrhage from falling off a couch onto a hard wooden floor?

Not usually: I'm not going to say this could never happen, as it is a possibility in people who are prone to retinal tears/detachments like with Still's disease. But for a normal child this distance fall is extremely unlikely to do anything more than a big bump and bruise superficially, and possibly a tiny headache for a few hours.

Very unlikely: Retinal hemorrhage is suggestive of nonaccidental injury.