Spruces made by me for a visualization project.
They consist of identical trunks with top twigs and three particle systems attached to the trunks, creating lower and upper branches and twigs. The branches and twigs are entirely made of image planes. The branch distribution is controlled by three textures, so you may alter the shape of the trees quite easily.
The spruces itself are also distributed by a particle system attached to a plane, so each spruce is created with a different seed. (Note that you must always multiply the overall amount of spruces with 100 to get the amount for each of the branch particle systems) The trees lack some realism in close-ups, but I think they'll look fine as a background scenery, where they catch and filter the light in quite a charming way.
The bark texture is from openfootage.net (by Markus Huber and Petra Hinterberger)