I noticed while expanding nodes in an AsyncTree that you can see the top 2px of the loading.gif repeat. Verified this occurrence in both IE and FF.
Figured it would be a quick fix and added a "no-repeat" to ~ln 43 in tree.css and ~ln 2030 in ext-all.css
background:transparent url(../images/default/tree/loading.gif) no-repeat !important;
However, after clearing cache and a hard refresh, it still shows the bg image repeating