Easy Textures - Coal

Start with a new image, Size 300x300.
Background Color: White, 16 Million Colors.

Step 1:
Choose Image - Special Filters - Add Noise.
Choose Random - 100 % Noise.
Do the same procedure one more time.

Step 2:
Choose Colors - Greyscale.
Then Colors - Increase Color Depth - 16 Million colors.

Step 3:
Image - Edge Filters - Edge Enhance More.

Step 4:
Set Foreground color to White.
Choose Image - Special Effects - Hot Wax Coating.

Step 5:
Choose Image - Resample - Custom size 150x150.

You may sharpen it if you want a brighter effect.

If you are going to use it as background, click here to see the result.
I didnīt do anything to make it seamless.