I am not sure for the right terminology, I guess the name is sprite. It is the texture which always faces the camera so it is like character in some 2D side scroller.
It happens in almost every game i know. If there is enough sprites it lags, otherwise it is fine.
I wonder, is there a way to make it fast
Like removal of unseen sprites by frustrum culling or computing which sprites would be not necessary to render (for example when there is 100 of them in a row so in the end only 1 is visible); I hope computing which are not visible would not be slower than just drawing them 
... do You have some experience with it?
