There are two things that will greatly affect your framerate there. The graphics of the sprites, and the collision checks. If your images are large in pixel size, has plenty of transparent areas, and any effects, it will slow down your framerate. Having a few of them is ok, having 25 of them you will probably notice some lag. Try to keep your collision checks down to the minimum that you can. It too has a big effect on your framerate if there is a huge amount of them.