Okay, then I focus on the arcs for now.
One last thing, How HQ do you want them to be ?
The pillar I already created is low-poly, rather LQ ( model-built-wise, not to mention the texture is too small to make them look good in a close focus)
However, for the arcs it is important to know whether they should be low-poly or high-poly
( low-poly = low file-size, but drawbacks when it comes to look
high-poly = not as edgy as low-poly, but much higher file-size)
About natural stuff, like plants, the textures are too small, the only thing I could do is add alpha channel and make them a 2D plane, simulating they are 3D ( most small plants are concepted this way in wc3)