Douglas, Balsam, and Frasier Firs No to all these unless they are dwarfs you work in later. Focus on cultivars of Abies koreana and Abies concolor. For any fir you NEED well drained soil. Pines (Jack, Red) No to these. Focus on cultivars of P. strobus, P. cembra and P. koraiensis. Spruce Limit the use of Picea pungens. Utilze Picea abies (smaller forms), Picea orientalis, Picea glauca and Picea omorika. There are several other species to look at once you start going to dwarf forms. No offense to the folks on the design forum but some of them are too wrapped up in "rules" of design. Do what works for you and take everything else with a grain of salt.

When are you planting and are you watering the trees after planting? Are they mulched? Are you putting down fertilizer / root stimulator / miracle grow or ammending the soil? Are you planting the trees too deep or can you see the rootflare about the soil?

I was admiring a pair of Arbutus a couple of weeks ago. They were planted over ground cover so fruit drop and bird poop were not a problem. Crape myrtle, on the other hand seem to mildew badly for me, here in Orange. Of course, my favorite tree is probably not a good choice, but if you have the right conditions, a coast live oak is a fine tree. When we moved into our house in February, 2005 I almost pulled up a "weed" in the parking strip which was actually a newly sprouted acorn that still had seed leaves and only four true leaves. I left it alone and shut off the sprinklers to the juniper in that strip (not so good for the junipers). By early spring, 2011 it had grown into a bush about 6' tall. The city came out to trim the sweet gums in our neighborhood about that time. One of the sweet gums in the other parking strip was diseased and planted too close to the sewer line. However, before it could be cut down, the city forester had to come out and sign off on the plan. Well indeed he did the next day. I was sure that my oak would be toast once he saw the tree growing in my (really the city's) parking strip. To my amusement, however, he took one look at the oak bush, pulled his pruning shears out of a pocket, and limbed it up into a tree. He didn't mind the contraband tree as long as it wasn't badly grown. My baby had grown up. It's actually about 8' tall this year and starting to look like a tree. I'm prejudiced, but I think it's beautiful. There are no other oaks in the neighborhood so it's origin is a mystery.

Those grow pretty fast when happy and get big, so unless it is too close to pavement that might fit the bill. Whatever you plant you will have to wait years for it to fill the space.