Well, I just took a look at your forest tileset, and I am disgusted. The trees are all wrong. Not the way you have them display, but the trees themselves. Conifer forests have quite a deal of variety, and, for the most part, the trees will be farther apart in a healthy forest. (Otherwise, a fire would burn the whole thing down). Not only that, but the trunks are far too think for conifers. Mix in the fact that all of the trees are of a homogeneous size, and you get a very strange effect. (e.g. you need different sizes, saplings, more types of trees, thinner trunks, and maybe a few more dead trees stuck in the mix)