It seems I am at fault... I created a fresh new XIB, and made sure to select device family 'iPad', and the image is now showing up properly. I didn't think that was the problem because you cannot change the device family after creating the XIB! I looked everywhere for that options, but never found it... Seeing the raw XIB files, you can do this change manually, I guess (Notice where it says ".iPad"):
<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="4514" systemVersion="12F45" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none">
<document type="com.apple.InterfaceBuilder3.CocoaTouch.iPad.XIB" version="3.0" toolsVersion="4514" systemVersion="12F45" targetRuntime="iOS.CocoaTouch.iPad" propertyAccessControl="none">
Yeah, I actually solved it, and the problem is super crazy. The artist had set all the assets as "iPad" assets, so the Contents.json file inside the *.imageset folder was assigning the "ipad" to the images I have. I opened the json file in sublime text, and changed the "ipad" to "universal", and BOOM. I had Xcode open on the side, and the image showed up almost instantly in IB!! Like, wth...