so far we have to do that ourselves, get a picture downscale it, upload it and place it as a link , you need entry level photoshop and html , then you can build a preset worflow and automate , it will take you 5 minutes for 3 images tops. I use www.steemimg.com for image hosting and the markdown guide should do the rest.
I think the first image is the thumbnail for the post.
And good idea on the sharing side, you have some ideas all I was thinking of were solutions and how to make it happen. But it's a interesting addition, I'm thinking it will come later , but sooner is better.
Thank you for the reply, however, you completely missed the point.
It is not that the first image is the thumbnail, it is the first image is used to create the thumbnail.
The first image (or the image placed in H1) is the one used for the thumbnail, and is run through a resizing script on steemit.com
steemimg.com saves, automatically, three sizes of your photo. One is a thumbnail.
But, the only way, currently to use the thumbnail sized image, is to place the thumbnail sized image as the first thing in your post.
Which will usually jack up the looks of your post.