If the crashes happen randomly as you say, they are unrelated to the texture size and have some other reason. There are some common suggestions in the manual under "Troubleshooting" how to handle such problems. If the crashes happen more often when you add large textures, it can be a memory issue. DirectX crashes when the memory runs low. In that case you must limit the memory footprint of your game. Professional games use a compressed format for large textures.