Here you can find tools and other suggestions.
Tools to design games
Unity It is a platform for game development. Use Unity to build high quality 3D and 2D games, for mobile devices, VR / AR, consoles, etc.
Construct 2 is an HTML5 game creator designed specifically for 2D games. With it, it is possible that anyone can build games (it is not necessary to use code).
Scratch is a programming language that makes it easy to create your own interactive stories, animations, games, music and art.
Kodu is a visual programming language made specifically for the creation of games. The PC version is free, and for Xbox 360 the price is minimal.
These programs will help you create graphics: