As someone who is both new to Xenforo and just recently imported my vBulletin user albums using XFMG, let me assure you that you should have no problem doing this. The process is practically identical to when you originally imported from vBulletin to Xenforo. Plus, @Chris D provides great support should you encounter any problems.
I imported Albums from vB 4.2 (took about an hour) and it worked without error and let me save an import log. However, even after rebuilding and checking permissions - no content in the Media section appears?!?
Can you describe in a bit more detail what you can see? e.g. Do you see the Media tab or is that not visible at all? Or do you get to the Media index and see a permission error? Or that no media has been added?