If you haven't already noticed, the newer Little Math icon downloads now have thumbnail previews like Little Reader ones, like this:
(thanks, Sheeberi!)
All icon sets that were exported using the last beta build (Build 65) will have thumbnail preview pics.
On the Forum download page, this means that the downloads that were done on or before Feb 18th do not have any previews. In this case, I would highly recommend that you re-export your icon sets and upload it again, so they will be more eye-catching for other members!
Thanks!