Looks good so far

Ithaqua?

You can run the LISTIMAGENAMESDWG command to do this. It will list all the images in a drawing, and tell you if it is a fill style image (bmpsty) or a symbol/inserted image (pictr2)

You can also use my custom command that list images sorted by addon. Note that the accompanying data file is a bit out of date, so a lot of files will be identified as unknown add-on.

Personal textures are best put in a custom subdirectory under @bitmaps, such as @bitmaps\Tiles\Calibre

No matter where you put them, you will always have to tell CC3+ where to find them, CC3+ doesn't pick up new files automatically

Yes, the important things is the images on disk, not the symbol themselves inside CC3+.

Our second submission. Great work.

And yes, Quenten is right. It is your map, you can do with it as you please. Submitting it to the Atlas/Contest only means giving us the right to use it in those contexts, we're not imposing any usage limitations for your own maps.