For MediaWiki (recent comments | status changes | tags | authors | states | release notes | statistics)
Yay. I think this is a good addition and is towards making Special:NewFiles obsolete. It makes the table a bit crowded though (it already was).
What I don't understand is why you are renaming img_thumb to thumb?
It basically is a fake table column. The way Special:Listfiles and the underlying TablePager works, is that each column in the HTML table should correspond to a column in the database table. formatValue() will be called for each field, and only with the current field. For a thumbnail we need to know img_name, and as such we need a hack to rename thumb to thumb as img_name.
The table could use a UI designer indeed.
Also I was thinking that this page should be listed in the top navigation bar next to "my contributions" as "my uploads"
That explains it indeed.
I'm not sure if new top-level item is the best option, maybe it should be integrated to my contributions in some way or another.