Hi Asaf,
Based on this need, I'm building a downloader tool (as a volunteer; this
isn't done in my WMF role) to help create such
collections of
reduced-resolution (any size you want) images for a given Commons
category. It's not quite ready for use, but in the meantime I've created
the collection you wanted in the size you specified. It is 157 megabytes
in size, and you can download it (in a 7-Zip[1] archive) from here[2].
You might want to check out my CommonsDownloader <
https://github.com/Commonists/CommonsDownloader>
It quite does that, except for the category thing but it would be fairly
trivial to add.
Java users may also be interested in Édouard Hue implementation
<https://github.com/edouardhue/commons-downloader>
--
Jean-Fred