[Plugin: Ad Buttons] A few questions

Hi this is a nicely designed plugin, thank you. Is there a way for it to support multiple instances? So far it seems it can only be used on one sidebar, which is not good for sidebars that change depending on the page.

Some feature requests would be the ability to modify the image used for the “your ad here” button.

When you want to display 4 ads, but only upload 1 or 2, there are blank spaces. Could you make it so the “your ad here” button replaces any existing empty spot?

http://wordpress.org/extend/plugins/ad-buttons/