myself I love your mantle the way it is..just my opinion..as for the decor, it depends on the style, my guess is that you are going somewhat rustic with a tad contemporary..am i right? I think i would find 2 long narrow matching pictures or mirrors or pieces of art and center one on each side wall of the fireplace above the mantle, one thing that really looks great is to layer..so if you use mirors or if you use an outdoor scene ..say with a lot of grasses..you could layer your grasses in front of and below the art on the wall..to tie in the art to the mantle, and then add a few other outdoorsy things to the mantle..the photographs are too small for there, put them somewhere else..although lovely they are just not the right scale.. do you happen to have a rock collection? it would be pretty on the mantle with an outdoor picture of a stream going over rocks along a meadow? with the grasses.. or a few beautiful unusual rocks on the mantle with the grasses..or a hurricane lamp with washed river stones filling it..clear glass..to tie in the rocks of the fireplace with your art. tell a story about what you like, if you love horses a horse running through a meadow, if you love old mills, an old mill with a creek and some old wooden architechtural pieces.. a tall grouping might work in the center going down to a shorter one on each side..or a tall one on each side of each wall with shorter in the center.. maybe two long art or mirror pieces, a much taller grass in the corner center and the smaller grasses just over the edges of the art on each side.. there are number of ways to do this..but you love it..leave it white unless you hate the white..i don't..i think white and stones is very updated rustic

Groveraxle's arrangement on the mantle is perfect! Can you remove and/or adjust the shelving, e.g. maybe only two shelves on the left and three on the right? On the top left shelf you could have then have two objects and on the bottom shelf three taller (a single and a pair). On the right shelves two objects on top, one in the middle and two on the bottom....or something along this line to keep it really simple and give each of the items space for visual impact against the the wood backdrop. You have lots of nice items to choose from and it would be fun to see things displayed a bit differently.

One very simple idea would be to lean a couple of pictures (in different sizes) together on one side, then use your glass jar or any decoration on the other. Or one big piece of art in the middle. Doing this would look nice, while not covering your decorative trim. A take on these ideas (not exactly as these, but to give an idea):

I worry that if you hang the photo in the mddle of the wall you will not be able to see it as well. Is the piece of fabric the same size as the photo? If yes can you try moving it over to the right so we can just see what it looks like higher than when the photo was hanging on the existing nail? Then just for fun put the smaller of your bigger plants from beside the TV on the mantle to visualize what a vignette of three would look like…fireplace, photo and object to be determined.…and send another picture. Thanks.