Since oxidation is the primary concern in storage of photochemicals anything used to displace air (oxygen) would seem to be beneficial. The chemical makeup of propane is C3H8 and does not contain any oxygen in and of itself.
However, in this instance there are factors which must be weighed. Among those is safety. Propane is a flammable substance. Any usage of propane should be prudent and within the parameters for which it is intended.
There are other gases which are capable of displacing oxygen and possessing of a far greater degree of safety. Among those would be nitrogen and argon.