Easy Textures - Hot Lava

For this one, you need the plugin filter "Sandy´s Filters" by Sandy Blair. Download it here (67 kb). This filter is free. For installation instructions, go to the Filters Installation page.

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 - Special Filters - Erode.

Step 4:
Image - Special Filters - Dilate.
Do this two times.

Step 5:
Set Foreground color to White.
Choose Image - Special Effects - Hot Wax Coating.

Step 6:
Choose Image - Plug-in Filters - Ecosse - False Colours 3.
Use the default settings.

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

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