Conifers are certainly not all that matters. Beautiful bonsai is what matters.i have dug a couple of Russian olive this fall and hope that they grow as good as yours. Will post pictures later.
Someone asked about Russian Olive as bonsai earlier in this thread; I haven't had this one very long, but I think they are very promising bonsai candidates.
This is a Russian Olive (Elaeagnus Angustifolia), that I dug this spring. The first picture is just over two months after collection. The second picture is less than one month after that!
This one is a Quaking Aspen (Populus tremuloides), chewed on by beavers over multiple years.