Describe your suggestion...

Using the optifine random texture method to add paintings does not seem to work as expected, and would allow for additional paintings to be added easily.

this array of files should result in "alban" being replaced at random when it's placed

Does another mod also do this?

Unsure.

Does OptiFine do this?
Yes, it should. See here:

https://github.com/sp614x/optifine/blob/master/OptiFineDoc/doc/random_entities.properties#L24

resolved in version 4.5.0