Almost works as I expect, thanks, but ..
Having selected 'Just on selected screens', on all screen types except Page and Single Post (article) an instance of the message box appears at the top as well as in the correct place, messing up the website header layout. If repeat is on, multiple copies appear in the header. I would like to be able to use this plugin on Archives and Tags, but have to switch them off for the result to be OK.
This is seen on both WP 3.5.1 (Esplanade theme) and 3.4.2 (Coraline) - i.e. tried on two sites. Neither of these particular sites has an image in the header (and they happen to be on different, but very similar, web hosts).
Any suggestions, or is this a bug? Thanks.