Last time I showed you this photo:
Trying to keep things simple, I would identify the following Element Relations in a frame:
Relations based on Size are pretty straightforward. We are talking about two elements* that might be either equal or different in phenomenal size. Notice the use of the word "phenomenal". Remember, we are not talking about depth yet, we're still in an entirely flat world. In the example image above, both main elements (the tree and the building) are approximately equal in size. The building is bit bulkier, but the tree is a bit taller - and so there is equilibrium.
*once again: an element is not a subject. There can be only one subject in an image. It might cover a tiny portion of the frame, or it might cover a pretty large part of it. But there can be only one subject. In the image above, the subject is the tree and the building; you could perhaps phrase it better like this: the subject of the image above is the tension between the tree and the building
Orientation is also important.Remaining on the same example, the lines of tree and building are largely parallel; the two elements are neither moving apart nor converging. What does that mean for the scene? Whatever it makes you feel! I know what it made me feel when I conceived and took this photo. But meaning is subjective. Your interpretation might or might not be similar to mine.
Luminosity is also basically straightforward, but with an important detail: unless we're talking about a black and white image, your eyes can deceive you. Especially when we're viewing, say, a dull grey element next to a powerfully vibrant red. But colors being mostly of similar saturation values, a bright versus a dark element carries specific connotations. Once again, not I nor anyone else can tell you what that means. Sure, we all carry personal "ideologies" if I could call them like that; cultural and social influences, where dark means sinister, nebulous, suspicious, evil, and white means pure, innocent, good, and what not. But all these can come upside down in art in a matter of instants. On our example, the building is somewhat brighter than the tree - and your eyes almost instinctively fall on it first before they move onto the tree.
Color, is another relation factor. Like I already mentioned above, a vibrant red will carry a much different weight than a dull grey. Again, there is a multitude of connotations that can be drawn; a riot of meaning, based both on color symbolism (latent or explicit) but also on saturation difference, as explained earlier. On our example, saturation values are equally vibrant.
Texture, finally, is an even trickier factor. It's impossible to predict what it might mean in a scene. Unlike color or luminosity - dark=evil, white=pure - there is no blanket approach for texture. A highly textured surface might draw more attention; or it might not. A highly textured surface might feel dirtier than a smooth one; or it might not. You should be aware that texture is a factor that can create a relation between elements, but what that would mean becomes visible (maybe!) only within the context of a specific scene. In the example photo, the tree is clearly more textured.
Putting all these elements together, we see that the elements of our example photo stand in relative balance. None is particularly more prominent than the other, and whatever tilting of the scale toward one or the other direction is minimal. What does that mean? Once again, it's up to the viewer to decide! I know what it means for me.