In the ini file, the reference needs to be renamed for OD2
In OD1, the line would be f.ex:
PlusImage = Backgrounds\Xandar tabbed\Plus.png
MinusImage = Backgrounds\Xandar tabbed\Minus.png
For OD2, you would write:
PlusImage = Plus.png
MinusImage = Minus.png
I always do my tabbed docks with versions for both OD1 and OD2 (you just copy the ini, make the changes and rename it to background2.ini and put it in the same folder) You need to also change the name in the INFO section as well to reflect that it's for OD2, of course.