Create a new document in RVB, transparent background : 400 x400 pixels for example.

First, you need to set up your FOREGROUND color with the parameters you can see here.

R : 101

G : 31

B : 11

FILL your document with the foreground color (EDIT/FILL).

Then, set up your BACKGROUND color with the parameters you can see here.

R : 44

G : 20

B : 7

Choose under your filters, RENDER->CLOUDS.

Now, add a little grain:

Under your filters, choose Texture->Grain

Intensity : 50

Contrast : 56

Grain Type : Speckle

Under your filters:

SHARPEN->Unsharp Mask

Amount : 459

Radius : 4,9

Threshold : 31

Under your filters:

Artistic->Dry brush

Brush Size: 0

Brush Detail: 2

Texture : 2

Under your filters:

NOISE->Add Noise

Amount : 10

Distribution : Gaussian

With Monochromatic

Under your filters:

Artistic->Rough Pastels

Stroke length : 2

Stroke Detail : 10

Texture : sandstone

Scalling : 193%

Relief : 5

Light direction : Bottom