As a want to be artist, are there rub on patterns for rock painting?

Yes. Check out michaels or hobby lobby for rub on pictures.

You can also make your own. Use any line artbpicture from clipart or printed paper, and print and cut it out. This will give you the outside edge of the image. With small scissors, cut out the lines and you will have created a paper stencil. Or draw over the lines with a transferable, washable material e.g. colored wax from an old candle, charcoal, artist pencil, then turning it over, rub on the back to transfer the image.

I think this site may have the info you are looking for: http://paintingrocks.blogspot.com/2013/07/rock-painting-technique-pattern-tracing.html

browse through here for a positive inspiration.https://www.pinterest.com/pin/320459329725666081/?lp=true

How about simle dot painting?

http://colorful-crafts.com/mandala-stones-diy/

Tyvm

You could also use stencils and paint.