In my personal opinion I think it needs one of two things:
Something in the center to fill up that gap, filling up the final third OR Just have the picture with the dog(s) on one side side, I've often found (and been told by many people much better than I) that photographs an often look good if there is something on just one side of the frame, but It never works if there is a subject on both sides but nothing in the middle.
Also, I find the extremely bright background and the tree quite distracting, but then that could be due to how there's nothing in the middle so my eye is immediately being drawn to that bright area
As others have said, the tree brings the eye to the right dog; in addition, if it were not for the tree, it would be very hard for your eye to "decide" which dog is the subject; it is better to have one place where the eye is drawn, like moving them closer together as one subject.
Your foreground is off as well as your background. The depth-of-field is also off. If you can see what I see in the middle, the faces of both dogs are off blur, meaning the are blurry. Also the faces are over exposed a touch, there is a good distance between the dogs. I will download this and edit the way I think it should look and show you what I'm talking about.
I don't know that it's the composition as much as the brightness of the background. Because there's a space in the middle and that area of the image is super-bright, that's where the eye is drawn to but there isn't anything there. If that makes sense
I love this photo! The only thing that I dislike is the difference of the angles of the dogs. I think the picture would've been even better had the left dog been looking at the camera the same way the right dog is. Keep up the great work!!
Only you can truly know what the photo is missing. However, composition-wise what you have is symmetrical-- which tends to be bland. If the dogs could be posed in a way that created variety (such as one laying on ground next to the other sitting up) it may prove to be more dynamic and lively.
In this particular case, assuming you have control of the dogs, you should: 1. Move to a position where you don't have bright light behind the dogs (a neutral gray or green is better - still light but not bright). This would also fix the tree issue. 2. Get the dogs closer together. Too much negative space in the middle is bad. At least if negative space was on the side, you could still crop.
But ... 1. Great detail on the faces, and a catch light in the eyes. 2. Good low-to-the-ground vantage point.
Id bring down some of the greens, Whats happening here is your eye is going directly to the brightest colors the dogs really dont have much color on them so in a way your eyes is focusing on the part that isnt focused. Id try to desat the greans a bit and add a bit more contrast to the dogs. here something like this [link] i did it a bit quick just to give u the idea of what i mean let me know if this helps
I think if you cropped it so the space between each dog's head and the end of the frame is equal, it might feel better. You could also bring them closer together by just cutting out some of the empty space in the middle and blend it together since the background is basically just out of focus blobs. It'd be not too hard. No blades of grass or such to deal with.
The only problem is the tree sticking out of the dog's head. The dog where the eye immediately goes to. But, I'm not sure it's really a problem in this case as there is a natural line around that dogs head.
Now, if you intended for both dogs to be the subject or the other dog to be the subject, I suppose that would be compositionally wrong. The white on black contrast of the nose on the right dog is just too much of a draw to the eye.
I am not a photographer but from an artists' point of view, the one thing that I notice is the tree in the background, behind the one dog's head, I find it very distracting. And perhaps the spacing of the dogs. But it is a very nice photograph. Lovely dogs.