The major problem with the approach of targeting "carousel keywords" is that .. Your images can be taken by anyone else who is also targeting the same keywords..and Google may well show their stolen image not yours..so you won't get even the eventual ( after Google force the additional pages and modal "lightbox type" pages with ads in front of the searcher ) visitor..and you won't even know that it is happening due to personalisation..
So is that game over for webmasters? Do we turn the lights off?
There does come a point where it is no longer in the interests of any webmaster to just smile and take it in the hope of the occasional searcher who makes it past all of "Google's interstitials" from the link in SERPS to their pages..If Google were doing this with text descriptions there would be uproar all over the net...
If your text content could be copied by anyone, and their description or snippet in SERPS served up by Google instead of yours, and if Google said that the content was "from the web" ( an admission by omission that it probably wasn't from the original creator , but was scraped )..and if the click on that "description/snippet" resulted in yet another Google page opening with yet more ads..and a click on a link on that page resulted in yet another Google page with yet more ads ..and finally a click on that page opened into a framed by Google page with yet more ads.. ( and the page content was greyed out with a "this may be subject to copyright" <= of course it is subject to copyright..and Google is not the owner, nor is it "fair use")..if that was happening, then all webmasters would be in uproar..and lawsuits for IP infringement would be flying all around the plex..
Because what they are doing with ""carousel" is illegal, unless they are certain that the images are copyright free such as those from wikipedia..
They cannot say..block us with robots text..because they are stealing second hand..apparently they have taken a leaf from the pinterest book and decided to crowd source the IP abuse and so try to play the "it isn't our fault we just found it" card..so webmasters have no defence..
Discussing methods to SEO for carousel is like saying to victims of sexual assault in their own homes, that they may as well enjoy it, because the perpetrator is too strong, well connected, will do it again..and that they should discuss which lipstick and makeup and clothing the perp prefers and try to wear them..because when the perp has finished..they might just say what a good time they had and send others.. around to the house..
No good saying that they can lock the doors when they see the perp coming, because the new method is anyone visiting may just take pictures and G will use them not caring who owns them..but knowing full well that G themselves do not..
G is now adding IP theft by unknown proxy, to what was previously search engine crawling..
The only thing one can do outside of closing all ones image websites and or showing no images at all to anyone..is now to watermark absolutely every image..