Paint brush posts
Here the rotunda could be converted to a paint pot, and the pole next to it to either a pencil or paintbrush.
Chalk
The plaza here could be used as a giant canvas, with chalks handed out so passers by could create their own, temporary art works.
Humanoid
The structure at the front of the building reminds me of a giant with its mouth open and fists held up at shoulder level. It could be painted to make this more apparent, and visitors and staff would be 'eaten' as they enter.
Ceiling drawing
I noticed that the indentations were of similar proportions to a wide-screen monitor, and thought that pictures could be attached here.
Paint pot fountain
The fountain part of the sundial could be converted into a paint pot, with the metal part made into a brush.
