But generally, maybe you can swap out "mediocre photos" with "better" ones either by yourself, or by others who gave you permission? Not because your photos are so bad, but because there are sweeet photos out there, from photographers who would love to help / show off - and photos that "say something" would help drawing people in, and keeping them reading.
I'm thinking of the Luminous Landscape (google it, explore it, wear it like a funny hat) here, which tends to have articles that explain something, and then a photo that illustrates the technique -- but without talking a whole lot about that specific photo. Maybe you can draw some inspiration from that, and try to "decouple" the photos and the articles if you will?
I'm saying this because I LOVE the general idea of the site, and that it's without clutter (though personally I think the font sizes are a bit huge). It's bookmarked to help out newbies when I run into them; now if you kindly could turn it into the best there could possibly be? Thanks :) I like what you're trying to do, and wish you all the best doing it.
Oh, and I think the whole point about art is a bit, uhm, besides the point. Yes, if you want to make great photos you don't read about shutter speed -- at the same time, if you want to learn about shutter speed a book of art photographs is perfectly useless, too :P
As for using others' photos...there's a couple reasons, and they don't have to deal with personal pride. 1) Distribution /copyright issues, 2) I would spend waaaay too long if I felt I had to pick the best of the best out there (even among just the Wikicommons material)...plus, I'd have almost no expertise to share about them, so I'd feel a little guilty about using them mostly as eye candy.
I think my direction will be to improve the quality of the photos, but more importantly, improve the relevance of the photos to the topic at hand...I don't think I'll ever satisfy everyone's idea of what a great picture is, but at least I can put up educational ones.
Instead, I think LL tends to pander more to the pixelpeeping crowd. Just my opinion. There are much better sources to learn to take better pictures.