This subject has come up a few times on the Technodrome (In my links on the right) So I thought I would post on the topic here...The Suject of Making loose figures stand.
Here are some tips from TMNTMan:
1) Make sure you have decent shelves. If the shelf isn't steady than the chances of figures toppling over is going to greatly increase.
But if that doesn't work
2) Fun Tack or museum wax. You can buy these items either online or in many hobby stores. A small dab under the feet will hold your figures in place and can be cleaned off later. Just be careful as some types may discolor the plastic over time
3) Stands/physical support If all else fails, and with some figures it will, you will need extra support. There are companies that make stands that plug into the holes in the feet of an action figure (if there are holes) The down side is they can be expensive and take up extra space. But there are alternatives. I found some small, powerful magnets that are just the right size for the peg holes in Marvel Legends figures. So now as long as I have a metal surface to put them on, they never fall over.
Here are some tips from Me!
1) Play with different positions of arms. Arm orientation can make all the difference in the world when it comes to balance.
2) The wider the stance, the better. When in doubt, spread their legs apart further. The lower the center of gravity for the figure, the better. Sure it might look a little odd, but if you have alot of figures clustered together, you wont notice their legs.
3) Use the arms of figures in the rear to support unstable figures in the front. Stick out the arm of a stable figure and prop a figure up against his fist. You'll never be able to tell from the front.
Thus Ends Your Lesson On Standing Action Figures!