All good ideas, Brat.
Ideally, people will send mostly larger pieces easily used by quilters of all skill levels (half yard or more, and large "scraps"- F8 size.) We definitely want to send out things that are usable.. maybe not, for example, selvages for this particular swap.
Anna- also a good point. I would say
no smaller than 2.5 inch squares, for sure. My original plan was for it to be a mystery box, but if you have more "trash" than you have room in the box, I see no problem with you getting input from your partner on what she'd like.
Kiffie- embellishments, notions, buttons, thread, books, patterns, anything like that is welcome as long as the box is mostly fabric. If you have a few things to tuck in, feel free. I'm sure your partner will enjoy it.