Here are some long dress design ideas:

1. Maxi Dress: A flowy, full-length dress that's perfect for summer days or evening events.

2. A-line Dress: A classic silhouette that is fitted at the top and flares out at the bottom.

3. Wrap Dress: A dress that is wrapped and tied around the waist, creating a flattering and feminine silhouette.

4. Mermaid Dress: A fitted dress that flares out at the bottom, resembling a mermaid's tail.

5. Empire Waist Dress: A dress with a high waistline that sits just below the bust, giving a longer and leaner look to the body.

6. Boho Dress: A loose, flowy dress with a bohemian flair, often featuring patterns and prints.

7. Sheath Dress: A simple, streamlined dress that hugs the body and is perfect for work or more formal events.

8. Ballgown Dress: A dramatic, full-skirted dress with a fitted bodice, perfect for weddings or formal occasions.

9. Halter Dress: A dress with a high neckline that ties or fastens around the neck, giving a flattering and elongated look to the body.

10. Off-the-Shoulder Dress: A dress with a neckline that sits off the shoulders, giving a feminine and romantic look.