I think Luke should be on the front cover next to Vader instead of Yoda anyways. It's the OT - this about Luke vs. Vader (well it's also a bit about Yoda vs. Palpatine, but that's more of a background theme, imho).

Edit: The "Final Conflict" one is my personal favorite, though. Because it solely shows Vader and somehow suggests that the 'final conflict' in this trilogy might also refer to the conflict within his tormented soul. Plus the simplicity of the design makes it stand out for me.