Just 1 index card mini deco for 1 partner.
You can send 2 or more if your partner is OK with more.
Booklet size: 2.5"x3" (use a 3"x5" index card or equivalent cardstock)
Established decos take priority. Only send a new deco if your partner has already filled (or is the creator of) the ICM decos you have.
New ICMs: Fold an index card (or card-weight paper - 3" x 5") in half to make a little 2.5" X 3" book cover.
Choose whatever theme you would like (including open-theme), sender's choice.
The front and back covers (and inside front and back covers if you choose) are yours to decorate and add info like your username, email, swap name, and return mailing address.
Include just 1 or 2 folded pages that are bound in the middle. I highly recommend only 1 folded sheet so the booklet doesn't get too thick to close. 1 folded sheet provides 4-6 pages to fill. Also the inner folded page should not be cardstock. Regular printer paper weighted paper works well. A few established ICMs that I've received were too thick to close, especially those with cardstock/index card for inner pages, and those that had 6-8 pages to fill.