It's not generally done, but easy enough.

Add a CLOUD sheet above all but the TEXT sheets, and add a largish blur effect to it. Then either add circles of pale colours (not all white), and/or use the freehand drawing tool with a line width set above zero to scrawl on that sheet in similar off-white colours.

Here is the smoke from a chimney stack done using scribbles and a blur.

Beautiful work, Ralf :)

No sweat.

Most of what I just said is available in more easily digestible bit-size pieces in the help tool you can open from within FT3, so you can take your time to learn stuff.

Exporting smaller regions might help a bit, though I'm not sure if it will help as much as you want it to. Whatever resolution the export is set to is the one you will get, whether its a whole world, or just a small continent.

I know :)

It's also quite common in other places too.

How interesting! It just goes to show that it pays to do a bit more research than a single Wiki page.

And yes - I think a seal with a seal on it would be just the sort of thing to make people smile on a dark damp day as they flick through the available stamps.