Looking at a particular dataset, and the related data at the bottom - the thumbnails used in this content don't seem to follow the rules of the other thumbnails across the hub site and arcgis.com. Is there any chance it could be changed? It's a minor thing, but we've created thumbnails per the rules (600x400 -- 1.5 ratio) that make them appear nicely in the arcgis.com item view and the search results and here they appear differently.
In particular, the element is styled to background-color: #ccc; via .connected-content .connected-card .left-pane
The image is sized via content .connected-card .left-pane img to
Thus a 1.3 ratio and grey back ground compared to the transparent and 1.5 ratio everywhere else.
We can look into improving this. This section of the app is a little bit older than other parts. The tricky bit is that we do have a number of customers using the old standard thumbnail size, which was a maximum resolution of 200x133 pixels. I think we can bump the aspect ratio up to ~1:4 in the short term and then map to the new standard during some improvements coming out early next year.
To answer your question on why there is a gray background? If one does not include a thumbnail with their item, we load a default thumbnail in and that is a white image with a transparent background. We were using the background color of the site, but then sometimes the white image would vanish on white sites. Gray was the most neutral for the largest array of customer themes.
This whole area could use a little work, but there are several major features ahead of it. I'll keep you posted.
Thank you, Klara.
None of these are show stoppers, but I had got a couple comments about the "strange" thumbnails in the related content. Nice to hear improvements might be happen in this area.