When you fractalise smooth polygons they become straight ones again, so you will have to make them smooth again if you want them to be smooth polygons.

That's good :)

To put the effect on the whole map add it with the Whole Drawing radio button selected.

Depending on the type of map you are making...

Dungeon style symbols are usually imported at 100 px per map unit

City symbols are usually imported at 40 px per map unit

Overland symbols are usually imported at 20 px per map unit.

So it really depends on what type of map and how big you want your shield.

Ah, I see.

Maybe generate a temporary grid using 'Hex or Square overlay' in the Draw menu, and count the squares?

CTRL+Z to undo the grid once you've counted.

Ok, thanks.

If you want to make the wall thicker, hide all the other sheets and use Change Properties on the wall alone, giving it a wider line width.

If you want to make the sheet effects more prominent (the glows and shadows), you can edit each effect singly to give them larger widths or blurs. To do that, open the Sheets and Effects dialoge and pick the sheet, then pick the effect you want to edit, and click the EDIT button on the right next to the effects panel.