Geh... Icons 42 - 49 are whatever you want them to be. The whole reason why none of the icons were named in the first place is because the icon slots are simply placeholders in which you can put whichever character in using the Custom CSS code. They don't actually have any value whatsoever as to what they contain. You could have 80 characters with 80 separate icons, but the only ones that those 51 icons would contain would be the ones you placed on the CSS.
Suppose you made a CSS that was made up of 8 characters. For this example I'll use Mario, Luigi, DK, Diddy, Link, Samus, Pikachu and Mario again. Assuming they are in the order that I mentioned them, the CSS data for the Custom CSS code would look something like this:
0009011A 02030800
as opposed to the original:
00010203 04050607
Now, the eight spaces which you guys have labeled Mario, DK, Link, Samus, Kirby, Fox, Pikachu and Marth in correspondence to the original values will become Mario, Luigi, DK, Diddy, Link, Samus, Pikachu and Mario - in that order. In a like manner, if you have a CSS with over 41 characters, icons 42 and beyond will become in use with whatever character was assigned to that slot.
Granted there is the question as to why those extra spaces are there in the first place, in which it would be a logical guess that they were indeed intended to the 7 unused characters and Mario D. (debug Mario) But having those extra slots there doesn't mean anything until sc_selcharacter.pac contains the respective icons for them to be used (I'm working on it, okay.) and that's not going anywhere until I can find a way to effectively solve the filesize problem.
Hmph. I'm feeling a bit cynical tonight, so please don't take offense to the presentation of this rambling fellow's words if they come across as being condescending or anything.