Is there a way of adding to the boxes that appear in the centre?

what i would like is a new box that i can turn on/off and place a sort order, in a way im looking at something that i can add and control from the index listing in the admin.

The reason i want this is, i want a graphic in a box to be at the top of every page, but to not to hard code it on the page, as i will need to turn it off and on at times

Any ideas on going about this would be appreciated

Cheers

Rob