We use old vintage suitcases stacked on top of each other and then store out of season clothing within. However, with your heat vent that might not be a good fit for your family.
What about a small open table? We have several small tables that have one shelf on them in addition to the top. Can put a basket on the shelf to catch small items that you like to be handy like lip balm or kleenex, etc. With the open shelf/ table the heat vent shouldn't be an issue, it can pass right thru/ around so long as you limit how much stuff you put on the shelf. You can paint to desired color.
Maybe something like this? (ramdomly grabbed a pitcure online)http://nakedfurnitureofmilwaukee.com...ble-p-681.html
We have 2 little tables like this, but our shelf is much higher thou, more like in the middle of the legs instead of at the bottom. Very handy and have been in different places all around the house over the years. Honestly, we found ours set out for trash in the alley, but maybe could find something like them at a thrift store or on Criagslist.
This Ikea link is more like what we have, ours are a bit bigger/longer instead of a squarish, more like a larger rectange and no drawer, but this is set up works great for us. I don't think ours are quite as tall as this one, but it's very like it.http://www.ikea.com/us/en/catalog/products/90121234
Plus, they are very versitile and can be used all around the house should your needs change over the years... plant stand, accent table, foyer table to catch keys, side tabel for the couch/ by a stand alone easy chair, etc, etc.