Using Ultimate Branding Plugin, I find that adding a banner image to footer deactivates or blocks the admin footer buttons on many admin pages.
I tried this in Safari, Firefox and Chrome.
If the banner is aligned left it often covers whatever admin button is in footer, but even if button is not covered by the banner, the button is not clickable.
Even if I try to add breaks (to push my banner lower), it still covers or deactivates admin footer buttons (if a particular admin page has a button way down in footer area).
I can get around this by hitting ENTER to submit an admin button of course, but still... I'd prefer the admin footer buttons to work properly.
Here is my footer banner code:
<br clear="all"><br clear="all">
<img src="http://imagehere.png" alt="Click to visit" width="600" height="94">