I've researched the process of making patterns ready for CNC plasma cutting. The key is to create a vector line drawing file in the DXF format. Here's how I've done it;
1) Use Microsoft Visio (part of the MS Office bundle) to create a black 1:1 silhouette pattern with the correct dimension holes and placement. I used a factory original Gamo faceplate to get the dimensions. Download animal silhouette JPG or PNG files from the internet. Insert the animal silhouette, scale to desired size, and overlay with the 'send to back' option in your Visio VSD file. This creates a solid black on white silhouette of the exact size and proportion you want the finished metal faceplate. It should fit on a single 8.5x11inch sheet. I can send you the hole pattern VSD file as a starting point.
2) Use the export option from Visio to create a PDF file of your conjoined silhouette and mounting hole bracket base.
3) Go to the vectorization.org website and browse your desired PDF file. This site provides a very simple converter from the PDF black on white silhouette to the vector line drawing in DXF format.
4) Download freeware DXFviewer.exe. This utility program will allow you to display the image stored in your DXF file.
Fortunately, I live in the middle of the rust belt with many small business and one-man shop metal fabricators. There are technical/vocational high schools in the area that can use plasma cutters to cut the DXF file pattern in 1/8" steel plate. I have created DXF files for animal shapes including bear, beaver, pigeon, rabbit, squirrel, and turtle. I'm working with a local metal fabricator to "print" the target faceplates. I created individual DXF files for each animal design with 40, 25, and 15 mm kill zones. Make certain to leave enough metal area to fully cover a 2.5" diameter circle centered on your kill zone, otherwise the knock-over paddle will be exposed at the edge of your faceplate.
The metal fabricator will provide me a quote shortly. He is willing to do small runs of a few targets to meet my needs. It's not my intent to create a side business for myself, but if the metal fabricator sees a small profit potential, he may be interested in making more. Once I've worked out any bugs with this process so I'm confident the DXF files are turnkey for any one with access to a plasma cutter to make successful copies, then I'll make the files available to interested members here. The process to make your own custom target faceplates is straightforward. You don't have to be a draftsman or machinist to make decent 1/8" thick GAMO alternative faceplates.
Post here or send me a personal message if you have questions.