People are creative and artistic. When you design a software control/widgets, you may use various graphical represenations (glyphs and icons) to represent certain things.
When you pick icons for "actions", you should try to pick one that general population are used to. This is even more important if your icon does not accompany any text. (By the way, do not rely on tooltip/popup text for explanation - if something had to be explained, then it is already hard to understand)
+ and - (plus and minus) signs are established for indicating "expand" and "collapse" actions.
< and > (left arrow and right arrows) are established for moving "forward" and "backword".
x is established for "closing" a window/panel.
It is best try not to invent new graphical reprentations.