Q:

Where can I get experimental versions of dropbox? 

Where can i get hold of the experimental versions of Dropbox for Ubuntu?  
Im looking for a version that allows the tray icons to be modified, and as far as im aware this functionality is only available in the latest versions. 
Thanks. 

A:

You can drop last experimental build from Dropbox Forum, here you can find the last version available, 0.8.110. 
Simply download your desired tar.gz and extract .dropbox-dist into your Home folder, than copy your desired icons in /home/yourname/.dropbox-dist/icons/hicolor/16x16/status.  Be careful to icons name.