SK, your first picture is of a bunch of nests. I'll show the same ones closer in a little bit.
The second picture is a large brush pile, mostly to the left of the boat. The dark part to the left is the radar shadow of it. Being right on a good drop, it should be a dandy spot for crappie. Don't know what that is in the 3rd and 4th.
Now let me show some of mine from the last trip out to the south end. Top left is down imaging, bottom left is normal sonar, right is side scan.
This one shows a little under the boat but the sonar and the down scan miss the big downed tree to the right.
This one shows scattered brush (not a pile) but clearly shows large arches in the sonar shot as arches.
This one shows limbs, but no fish.
Standing timber and fish arches in the sonar.
Don't see much structure other than the drop off, but sonar shows fish arches.
SK, these are the same things on the bottom that you said might be milk cartons. They are round fish nests I think.
Down inaging and radar, see no fish arches. "the" pile.
I am still not an expert, but I gave my best guess on each. Note that side scan and down imaging are narrow fans of sonar out and down. Therefore you will not see fish "arches" on them. The sonar is a cone shape in all directions down and this will generate fish arches.