For Roll20, I just drag the image onto the page. It's dealt well with size and bandwidth on its own. If the image export snaps to CC3 grid squares, then the mapping of Roll20 grids is pretty easy: how many grids wide is it? Bam.

Once I'm done doing this, I don't delete the image just in case I want to revisit it and not have to reimport and reposition it. However, simply hiding it where it is means that it's in the way. If you ever have to use "show all" sheets, it's back and in the way.

Instead, I move the image sheet to the bottom so it doesn't show, and it doesn't matter if it's visible. If I ever need it again, I can move it back to the top, and it will be in the same position and scale.

(edited step 4)

GIMP can select areas by color. You can select all white pixels on the image with one click. Maybe use a little tolerance to include your preferred shade of gray in the borders between white and black so it's not rough around the edges; it's a visible setting. Then add a layer mask based on that selection. White will then be transparent. You can save that as a PNG or put whatever color you want behind it with a fill of a other layer behind it.

Short answer:

1. GIMP

2. Select by color, click any white pixel

3. Menu: Layer, Mask, Add Layer Mask

4. Pick "selection" and check "invert selection" at the bottom.

Done!

I think this is great. I love the texture.

The only thing I suggest is to compare the length of the cliff's shadow with the shadow of, say, a building. I think the cliff shadow is too short.

Maybe that's a perspective thing. Most of the map is overhead, but the cliff is not. I'd say that if the cliff were narrower and the entrances were at a sharper angle, it would match even better.

These are just comments, as I think the map is really good.

Oh dear. Wow. The "Direct Download" from Humble Bundle is markedly different from the ProFantasy web site. I never used the HB direct links, so I didn't see what you saw. I very strongly suggest that you copy your HB keys and paste them into your Registration -> Downloads page, and then download the installers from there. I'm not sure if they just renamed the installers or if anything else changed. I personally wouldn't trust a download from anywhere but ProFantasy.

The ProFantasy route also has the benefit of always being there if you forget your keys, lose the installer, lose the SM PDF, or want an update.