Such an error can come from more than just the template (e.g. cyclic dependencies), could you provide a complete and minimal example with the template?
Secondly, is this class just for learning purposes or why aren't you using
std::pair?
And finally, you should not be storing a full texture that way. Textures are heavy resources. If you simply assign an texture to your tuple it will make a copy. Copying a texture is really a bad idea, because it involves moving the data from the VRAM to the RAM and back to the VRAM.
At best you should wrap the texture in a smart pointer (unique_ptr or shared_ptr), bundle it to your class/type with a std::pair and put it into a STL container.