It's a very tough decision between the other two, though. In the end, I'm putting Jim Burns' cover of Pelquin's Comet second. It's an arresting composition, but perhaps just a little less adventurous with colour and shade than my top choice, and also rather traditional in its subject matter - not that there is necessarily anything wrong with that, of course.
Which leaves Vincent Sammy's illustration for "Songbird" in Interzone as my top choice. I haven't read the story (and indeed haven't read Pelquin's Comet either, though I did read Jews vs Zombies), but this is the kind of illustration that challenges the reader to find out what the story is about, whereas the Burns piece seems pretty clear on that score. I find the composition pretty fascinating.
Presumably there are only three nominees due to a multiple tie in nomination votes for fourth place - this happened also in 2013 (when I ranked the eventual winner third out of three). I'm a bit surprised to see it repeated with the new two-stage process. Perhaps there was less voter input in this category than the others; if so, an opportunity to celebrate more good sf art has been missed.
Edited to add: Am locking out anonymous comments on this because it's been getting a weird amount of Japanese spam. You can log in using other OAuth identities if you want.