While developing my software, I realized this. After loading one of the shapes that are the same as the pictures to be used but the angle is different, I changed the angle only for the others. So, I uploaded less images.
As a graphics designer, I keep an aye on all these tricks and this will be fine, only if you don’t have to take the highlights and shadows in consideration. Most of the people don’t care or notice that kind of stuff. In that case you could use a different effect that makes the arrow look the same if inverted.