I bought picture rails like that at IKEA some years ago. They mount straight to the wall via a lip on the back which isn't too intrusive, and is mostly hidden when artwork is placed on them. Mine are painted the same color as my wall which I like the look of.

West Elm has some: http://tinyurl.com/6ho8y5

The first photo is of a ledge, not a shelf - the lower wall is deeper than the upper wall and the wood simply caps the ledge.

I can't be certain, but the second photo appears to be the same thing.

I made some for my shop using hollow core doors cut to whatever size you need then mounted them by sliding over a piece of would mounted to the wall.

i bought the white rails from CB2 - they're awesome. They have have lip in the back with place for a screw.

I second the comment on Ikea's shelves, they are simple and attractive - and best of all, cheap.

I second the CB2 picture rails. Very nice. Just a word of caution, though. Even though you like the look of thin ledges, if they're too thin, the pictures won't lean and will instead fall off the rails. I learned this the hard way when I tried to pair the CB2 ledges with Ikea Ribba frames. Even when I backed the pictures with adhesive putty, the thickness and the weight of the frames made them come crashing down.

room and board has several options for picture rails in wood tones, raw steel, and powder coat.

it is really more about how you put it on the wall and less about the shelf.

How do Lack shelves mount? Can you figure that out then replicate that with a thin piece of wood from Home Dept or Lowe's?

Lack shelves from Ikea mount with a metal bar with two metal prongs that stick into the shelf. I love the look of the Lack shelves, but you really can't put much weight on them (or any other of these shelves/ledges that I've seen). I ended up adding the L-supports to mine.

Depending on how thin you want your shelves to be this idea might work for you.
http://www.wikihow.com/Build-Simple-Floating-Shelves
The thing that makes this style of shelf strong is the way it is mounted, the full length cleat is screwed to the studs in the wall, and then the shelf is slipped over the cleat and glued in place. Permanently. the similar look to the Lack style shelf, but waaay stronger and able to hold full shelves of books.

We have three six-foot Ikea LACK shelves hung side-by-side-by-side and fully lined with books, with no sagging or risk of falling.

The trick: first, run a 1x4 across the wall (or in our case two, mitered to meet smoothly in the center of the 18-foot wall), screwing the 1x4 twice into each and every stud with beefy screws. Then paint the 1x4 to match the wall color, and it mostly disappears. Then mount the LACK into the 1x4 with wood screws.

No need to worry about whether yr anchors will hold in drywall, or whether you can line the LACK up to hit at least one stud. It's screwed securely into the 1x4, and because the 1x4 is painted to match the wall, it's hardly noticeable.

If you were really crafty you could hang the LACK exactly at the bottom of the 1x4 so that you really wouldn't see it, but we didn't think of this until about a year after we hung it, and we're fine with how it looks.

I live i the uk so I am not sure this is helpful but I used a company in London called the shelving company http://www.shelvingcompany.co.uk/ check them out they were brilliant and I got exactly what wanted.

Hi guys! I've put up plans for some nice thin floating shelves on my blog. Check them out here: Mike Made - Thin Floating Shelves. These aren't photo ledges, but actual thin floating shelves.