Instructions for this image:

1.  Draw gradient.  (Ctrl - J)   Default colors.  VertCenter Gradient.  256 x 256.

2.  Smooth Resize. (Ctr - R).  to Width 256 Height 64.

3.  Copy to Clipboard.  (Ctrl - C)

4.  Undo.  (Ctrl - Z)

5.  Erase to Black.  (Ctrl - K)

6.  Paste as Selection.  (Alt > E > P > S).  Leave at location 0, 0 and click to set in place.

7.  Paste as Selection.  (Alt > E > P > S).  Move to location 0, 128 and release to set in place.

8.  Rotate90.  (Ctrl - Alt - X)

9.  Paste as Selection.  (Alt > E > P > S).  Move to location -64, 0 and release to set in place.

10. Scroll left 64.  (Ctr - Alt - K)

11. Paste as Selection.  (Alt > E > P > S).  Move to location 64, 128 and release to set in place.

12. Rotate Seamless.  (Ctrl - Alt - S)