That's doable, but you'll need to export the map in sections to accomplish that. I've done up to 200,000 x 200,000 that way.

Thanks for posting this and making a tutorial for it.

I haven't heard of OpenSeadragon before (been using Zoomify myself) but it looks like it does the job very nicely and easily.

The actual rendering issue MAY be caused what we call transparency acne, but it was difficult to see on your screenshot, which is why I also asked you if it was different if you tried a 5k square export instead of a 10k. Basically, TA can happen on entities with an edge fade or bevel effect where some of the colors of the fill are identical to the background below them. This can cause "holes" in the texture at the points where they are identical, and the edge fade effect then extends these holes, sometimes to the point of the original texture almost disappearing. If it is TA, one way to work around it is to put another entity (a copy of the top one, with another fill, such as a solid color) on a sheet sandwiched between the two holding the entities.

Tools menu -> Options -> Pick cursor aparture

And after gaming with you for a while, they became even more careful? :)