Hello! My country has two location-based stamps and I would be happy if you could add one more. Here are my suggestions:

A stamp with our flag (red, yellow, blue)

Corvin Castle - one of the largest castles in Europe and is featured as one of the Seven Wonders of Romania

Rock sculpture of Decebalus - considered the tallest rock sculpture in Europe and the sixth largest in the world (featured as one of the Seven Wonders of Romania)

Peleș Castle - another castle featured as one of the Seven Wonders of Romania

Palace of Parliament - the heaviest building in the world and the second largest administrative building in the world (featured as one of the Seven Wonders of Romania)

The Sphinx of Romania - natural rock formation in the Bucegi Natural Park

Also, a special day stamp about:

Mărțișor - a celebration at the beginning of spring, on March the 1st in Romania and Moldova