Yes, the CAD part is the first step. Fusion 360 has a version that you can use for free for one year (https://www.autodesk.com/products/fusion-360/personal). Fusion is very user-friendly. Depending on your 3D printer, you can 3D print a picture (2D to 3D). Mine has that option (https://www.youtube.com/watch?v=Vic6PkCgYk8), so you basically can use Microsoft Word or any program to make your design. The only issue could be the dimensions, but if it is for fun then it is OK. Also, look for any picture and 3D print it.