In EagleCAD, turn off every layer except for Pads, Vias, tStop and bStop. Change the color of tStop and bStop so that all 4 layers have the same color.
Export to a dxf file by clicking on File > Run UPL > dxf.ulp, and use the settings below.
Import the dxf file into Rhino by clicking on File > Import, and use the settings below.
Working in the Top view, select All Objects and click on Edit > Explode to make them become curves. Then click on Dimension > Hatch and choose Solid.
Result
If you need multiple copies of the pattern, select All, then click on Edit > Groups > Group. Make the number of copies that you need by using Ctrl C and Ctrl V.
Result
Print this onto a transparency sheet.