What type of design project is most suitable for showcasing the beauty of Celtic letters?

The most suitable design project for showcasing the beauty of Celtic letters is a greeting card. Greeting cards often provide a medium for artistic expression that allows for creativity and decorative elements, which is ideal for highlighting the intricate and elaborate designs characteristic of Celtic calligraphy. The ornate detailing and patterns associated with Celtic letters can be effectively displayed in a compact format, making them visually impactful as part of a personal message or celebration.

In contrast, other options like a technical manual tend to prioritize clarity and function over aesthetic appeal, which would not serve the beauty of Celtic letters well. A historical document might have inherent significance but typically would not focus on artistic embellishments in the same way. An artistic mural could potentially highlight these letters beautifully, yet its expansive format may not focus on the individual letterforms as effectively as a greeting card does, where the detail can be appreciated up close.