I realize this is off-topic but just as a bug report, I tried to search for "cezanne watercolor" and it didn't understand, despite that you have watercolors by Cézanne. Also it wasn't clear whether watercolors were best found under "paintings" or "works on paper". I think you need to make it easier for non-computer people to find specific types of image.
It's an interesting observation. We built a full text semantic search in 2011 by reverse-indexing art search results from popular search engines and it could do things like "Cezanne watercolors" at ease.
We showed it to people and we found that one could easily trick the system with things like "Worst American Art Ever". That generates results, but shows the limits of a general semantic search in a narrow context.
Happy to hear any suggestions about how to make something like this both useful and not too easy to make look really silly.
It only works in that case. What if there's another work that is called "Cezanne's Favorite Watercolor", and we're just in the beginning of search hell :)
Same thing for us at Art.sy. We have humans doing targeted emails, with MailChimp.
Sendgrid is an SMTP relay with high deliverability. That's all it does. You can find who received what on the website, too. With MailChimp you have to setup lists and all that unnecessary stuff.
There's one big drawback to using both: we currently have to sync our users to MailChimp and sync MailChimp unsubscribes back. Hence we're going to get rid of MC eventually when we can build good enough UI to manage mass emails.