It's not an application setting as such.

If you look at it through Firebug, you'll see that it's actually a background image call 'rightTab.gif', which is set from your Theme.

You can probably override it in your custom.css to point at an image resource within your db, or copy and modify and existing theme.

 

That doesn't seem to work or at least I can't see how to make it work.

 

I added an image="/someimage.jpg" to the tabPanel tag but that just made the image appear to the left of the label text.

 

That's a foreground image.

try style="background-image:url('newRightTab.gif');"

In my experience, I've had much more joy using Dojo tabs instead of the XPages inbuilt ones.

 

Firstly, validation does not work across tabs (until you have loaded them for the first time) and they are rather slow and clunky when compared to the dojo ones. 

 

Here is an example of how smooth they can be without any page reloads (obviously, the initial page load is slightly slower).  I've played about with programatically selecting a tab and the 'closable' ones and they are really good.

 

 http://dojotoolkit.org/reference-guide/dijit/layout/TabContainer.html

 

I will look at the alternative dojo tabs because changing the actual background colour of the tab seems impossible.

 

Thanks