The beauty of forests is they can be adjusted into the future. So you have a start. I do feel the spacing comment is leggit. I'd also like to see in the ring around the biggest tree, another smaller caliper along the outside, to give more of a sense of depth of field. With the trees to the left of the biggest trunk, allow the new top growth to rise up higher than the ones on the right. This will give movement
from left to right which will allow the trees to be in sinc with their placement in the pot. You may consider adding a carpet of moss to take away that brand new "look". Once established ( the moss) I could see going thru the carpet and removing a path and covering with sand, so it looks like humans or animals have a habit of walking thru. A stone here and there along the path looks nice. again remember depth of field so rocks in the foreground are bigger then mid field and last one is even smaller....
I like larches as well as maples to make forests from. Often propagaters will springle seeds over rooting soil and some will land and root close together. I particularly like those to select from as they deal with the spacing concern and add that much more naturalism to the display. They take time to develop but well worth the effort.
If you decide to use any of my suggestions, would love to see a photographic update