Who wants to create a vBulletin 3.x to xenForo 1.0.x style importer? I thought it would be a great idea, yet I am not paying for it. Just a suggestion to better add to the appeal of the xenForo community. I do not expect anyone to do this, but might be a fun project and build reputation for a upcoming or well-known styler.
I imagine the most time consuming task would be the mapping. If somebody hasn't already done that, then that would be the first place to start with since even a typed up listing would be a start for those wishing to convert their vB 3.x styles over to XF.
The main challenge would be the fact that XenForo makes use of a wider palette than vBulletin 3 - a certain number of colours would have to be made up or derived by lightening and darkening values fetched from vBulletin, but in theory it's possible.