Well, most replies have already stated that it is not a good idea and some have listed why. Now then, another good reason, is that some leather is tanned with chemicals and salts, such as acid-tan process. These chemicals like to eat metal and your metal will not be the exception ....
A few weeks back, a friend of mine got a new rig for his Ruger Blackhawk, white grips and all. He has it displayed and you bet, it looks awesome. He asked this same question and I have given him the same answer. I told him to routinely monitor it's condition in order to head off any problems.
We all understand that it's your gun and you are certainly welcome to store it any way you want. ......
Just be watchful and;
Be Safe !!!