Creating a pointer to a vector of Images

it's also easier if you return a reference instead of a pointer like:

vector<ofImage> & GridElement::getImages(){
    return images;
}

that way you get a reference to the original object but still can use the normal syntax like:

grid.getImages()[i]

be aware that if you do:

vector<ofImage> images = grid.getImages();

you are doing a copy but you can always do:

vector<ofImage> & images = grid.getImages();

or even easier:

auto & images = grid.getImages();