Seriously as a European I do not know enough about HD+ radio but DAB radio can transmit pictures which until now is mostly used to transfer album covers.
In due time we will see this abused to hammer ads down our throats.
When the service was first implemented, that was a possibility. Now, the most we're likely to take advantage of it is to show you a display ad that matches with the current "over the air" ad that you're hearing. Advertisers aren't interested in selling on top of someone else's advertising, and programming doesn't want their displays messed with outside of commercial breaks.
Plus.. it's a pretty low value service and honestly not worth selling. Advertisers all want demographic driven sales now, so those channels aren't all that useful to us.
RadioDNS opens the door somewhat to this, because it can direct your radio to start a stream instead of listening "over the air." However, there, we're happy to be able to replace the over the air ads with programmatic digital ads and that sales channel really doesn't care about "additional display opportunities" either.
Be happy that radio is slow to implement standards, and usually too far behind the punch to get the expected return out of them. So.. just album art for the foreseeable future.