With Dorchester National Park, I initially started tracing from a photo, and using the land use and geography attributes to add contrasting colors (park=green, forest=dark green, scrub=yellow green etc.) In the original photo, the mountains were barren, except for some glaciers (which I converted to lakes).
After a few weeks of tracing with the photo, I discovered a more original way to render mountain ranges other than just tracing from a photo, and also better than relying on imagination alone.
First, you will need the JOSM editor with the PicLayer plug-in installed.
Next, cut a long sheet of tin foil (about 2-3 times longer than the width) and crumple it up. Carefully, unwrap it and flatten it out. Now you can shape it according to your needs: you can flatten some valleys or raise some high peaks, as you like.
Once you’re finished, take a photo of your new mountain range and upload it to your computer. Then, open JOSM. Next, open OGF in the location where you want to put your mountains. Click the ‘download’ button in JOSM. Copy and paste the OGF coordinates in the URL field (for those new to JOSM, make sure opengeofiction is your default site, not openstreetmap)
Next, click ‘Imagery’, then ‘New picture layer from file’. From here, you can select your mountain image. This opens the mountain image as a background layer to OGF. Click on ‘Windows’, then ‘Layers’. Here, you can edit the mountain image layer (you may need to resize, rotate, or adjust the transparency) or go straight to tracing by clicking ‘Data Layer 1’.
Scaling the mountains accurately might be tricky. Maybe there are some more experienced mappers here who can advise on the average size of mountains.
Hopefully, this will be helpful for those who would like to render mountains. One caveat is that this is VERY labor intensive, so you might want to stick to rendering a small area you think will be of particular interest, as opposed to a 100-mile-long range.

