Having larger pics helps a lot even (or especially) with a "how-to" as it illustrates the things you're describing and clarifies questions the reader might have. They don't have to be huge, it's just that thumbnail sized pics don't really allow the reader to make out much at all. The pics are good once you do the right click and view thing, and the size they're displayed at on the blog is good as thumbnails, they just need to be tied together as clickable thumbnail links. Currently it's a little weird as they the size they display at looks deceptively just like clickable thumbnails, and is also very bandwidth inefficient/wasteful as the page has to load all the full sized pics even though it's only displaying them as what might as well be thumbnails.
Re: the brickwork efficiancy issue, maybe make some texture stamps? Say, a 2"x2" square of negative brick pattern in epoxy that you can use to rapidly "carve" an entire side by stamping it into the foam.
Since the faces are meant to be murals, maybe troll through DeviantArt or Tumbler image archives for fantasy art (Tumblr image blog archives are amazing sources of aggregated reference pics). Medieval painting doesn't resemble photos, and the further back you go, the more sort of orthographic and abstracted it gets (though even the later Renaissance stuff isn't anything that could be mistaken for photos). Pre-20th century stuff tends not to crop aggressively (you don't see many full-frame face portraits, much less with 1/3 or more of the face actually outside the frame), and strongly favors a window/proscenium-style use of perspective. A big part of the "movie poster" effect in the photos used is the modern style perspective. Even if you backed up the cropping to a 3/4 portrait, it would still look anachronistic due to the focal length and angling in the pics.