Recently, the production of big games is expensive, and it is very difficult to gain attention from players. Although gamers' expectations are very high, game companies' resources are limited to maximize the quality of the games. Mod (game content editing) can be one of the solutions to this problem. It allows gamers satisfy themselves by creating and sharing their Mod. It increases the gamers' playing time and sales. However, few users have the knowledge and special ability to create Mods, so most gamers just use a Mod made by someone else. In this article, we propose a method to generate contents for 3D game objects and textures. Our method enables the construction of a three-dimensional object using the grown building footprints by the L-system or the combination of polygons, and it also provides a web-based interactive genetic algorithm interface to users for changing shapes. Furthermore, it also provides a function to evolve various texture images from an original texture file. We demonstrated the possibility of our systems using The Open Racing Car Simulator (TORCS). These results reveal that three-dimensional objects and textures can be created from our method by amateur users.