I have embossed on copper many times, as well as other materials, it is great fun. You can obtain tooling foil at a craft store like hobby lobby. I comes in different gauges or thicknesses, choose the heaviest thickness you can still work for your design. Tools can be anything-they sell special embossing tools but you can use orange sticks, chopsticks, dried up ink pens, pencil erasers, whatever seems to suit the need without scratching or puncturing the copper. Lay the copper on a soft surface-I use several craft foam sheets stacked up, but you can also use several thicknesses of newspaper. This allows the design to form. You can draw your design lightly onto the copper, or tape a paper template to the copper and cover that with a piece of waxed paper that will allow you to glide over the template with your tool. then simply press hard and trace the design. You can then turn the copper over and lightly trace the edges of the raised design to give it more sharpness. You can practice with aluminum foil pans before you start on the copper- simply buy a disposable roasting pan made from aluminum foil, cut out the bottom with ordinary scissors, flatten with a rolling pin or by scraping with a credit card or spatula and play! I used this material to create angel tree toppers for christmas this year, it is easy cheap and fun. Here is a link to a page with a project similar to what you want to do that might help.

Here is a link that might be useful: copper embossing

wow, thank you for all the information!!