I was momentarily cast down, but like all bad ideas that get recognized as bad ideas, this helped clarify my priorities (particularly this: I REALLY want eyeglasses on the cover) and cleared the way for better ideas, of which I quickly had four. If you'll forgive the self-indulgence, I'm going to analyze these four ideas the way we analyze cover ideas in-house, for first what they say about the book in and of itself and then how the covers might connect with my intended audience (adult writers of children's and YA literature). Pardon the lousy sketching and type design.

B., Right. I think of this as the McSweeney's cover, as it would be mostly the gracious, formal type that's used on the inside of the book, with three or so small images of eyeglasses between the lines, most likely photographs (though it would be neat to find a cartoonist who could draw all of these glasses for cheap, if their style suited the font and the book). I was thinking a conventional or cats'-eye pair of glasses up top, a set of 3-D specs in the middle, and a Groucho Marx set down at bottom, to convey all the different ways one can look at writing, and also hopefully the book's blend of both seriousness and fun. OTOH, a pair of Groucho Marx glasses may convey not "fun" but ridiculousness or absurdity. None of those images say "books" or "writing" or "editing" directly, so a potential book-buyer would have to read the text for that, which slows down the potential buyer's emotional reaction, which slows down their buying reaction. And the images are really small, which means the cover might not reproduce well online, where it could be an inch tall on a computer screen. And as online will be one of the two primary ways I'm selling this book, it's important that it be instantly visually readable. Hrmm.

D., Right: A plain background with floating type and a stock photo of a dachshund in oversized glasses. I adore dachshunds for their dignity in the face of their physical ridiculousness, and this image is so darling that I imagine it might get a lot of readers to pick up the book. Indeed, in that way, it would connect to Rule #1 of children's publishing: Cute dogs sell. But the image ultimately suffers the same lack of instant connection to the book's subject as B. above, and having a dachshund in oversized glasses on your front cover is not, perhaps, the best way to have your serious writing book taken seriously.
So of all of these options, I'm leaning towards A. -- or whatever my book designer will come up with, which will doubtless be much more original and all-around better than anything I've tossed out here. Anyone want to propose alternate concepts or change my mind?