Okiedokie, this all spread around faster than we thought it would considering it was posted in like... two Skype groups total. I suppose clarification is in order!
These icons are intended to be used for DLC; or at least, are placeholders for images that may eventually be used. Their filenames from left to right in the image are:
ym_CupIconDLC_00_130x130^h.bflim
ym_CupIconDLC_01_130x130^h.bflim
ym_CupIconDLC_02_130x130^h.bflim
ym_CupIconDLC_03_130x130^h.bflim
The "DLC" in each name can't really be mistaken. We haven't located the 3D versions that the menus use; but we haven't located any of the 3D cup icons in the first place, so there's no saying they don't exist. Mind you, in their current form, these icons are missing some files that complete cups have, namely some textures used for effects and similar. When we had the game render these, we had to use the mushroom/flower cup's effects, which might have caused small drawing errors. The other files might be downloaded someday if these cup icons are to be used for something!
Also supporting the DLC theory is that the valid track IDs in MK8 start at 0x10 and run to 0x2F. The ones before that, 0x00 - 0x0F are labelled as Reserved00 - Reserved15, exactly 16 slots that are apparently... "reserved". What's 4 x 4, I wonder? And what are they reserved for?
Furthermore, there are 16 full size graphics of 12 Marios on the start line of Mario Circuit, with the word "SAMPLE" plastered across. All of these images are labelled "DLC" as well and are probably placeholders that may one day be replaced with brand new track images.
Of course, we won't know for sure until Nintendo says something.
Also, interesting discoveries, there might be plans for a Shy Guy outfit for Mii, and a Yoshi outfit for Mii. There are placeholder files for those on the disc as well, but when we tried to load them, we merely got a red suited Mii. Very unfortunate. Still might be an indicator of things to come, though!