I think this is a huge flaw in the new blog platform in regards to the gallery UX.
In the old blog, the user could tap/click an image item and see that image full-screen. However, I found that it's not possible in the new one! This becomes a bigger issue when we take into consideration layouts like the 'collage' one. While I really welcome those new design, those few inevitably small images just remain small, with no way to enlarge it to see it in detail. It's a shame the gallery does not yet provide that!
I hope this is already on the list you're working on, and if not, I fully believe that this must be on the priority list for the new blog to be really useful.