Inkscape download here:
1. Open Inkscape, in the bottom right corner set Zoom to 100%, select Rectangle icon (Create rectangles and squares).
2. Create a rectangle, on the bottom colour panel, set Fill and Stroke to various shades of brown, right-click the colour to choose Fill or Stroke colour.
3. Make sure that you selected your rectangle, navigate to the top panel, choose Filters, category Textures, then Rough paper effect.
4. Again, make sure you have your rectangle selected, choose Filters again, category ABCs, then Diffuse light effect.
5. You need to save your project. Save it somewhere.
6. Now you are able to export the rectangle as a bitmap. You must save the whole project to be able to export any bitmaps with effects applied on.
Now, make sure the rectangle is selected.
Navigate to the top panel, choose File, then Export Bitmap... to export the rectangle as a .png file.
7. Everything's done! :-)
You can experiment and use different shapes (at least different from rectangles). Draw Bezier curves and straight lines tool is recommended. After closing a shape, simply fill it by choosing Object in the topmost panel, then Fill and Stroke sidepanel, then procceed with tutorial steps from the third one on, and up to the 6th one.