You should be able to see the textures in texture shading mode also.

Another thing to try if your scene is dark with texture shading mode active, is pressing Ctrl L which sets the light mode to Preview Lights as opposed to scene lights.

Nvidia Iray mode is great if you have the computer power to handle it, but it can be pretty resource intensive and may slow down with camera movement on a large scene as it is continuously renderering the scene.