It is not safe to store any combustible items in the clearance area around a wood pellet stove. Manufacturers designate minimum clearance distances to promote safe operation of the stove, but a larger clearance area is sometimes better for optimal performance.
In addition to keeping combustibles away from the stove, there are requirements for the flooring under it. The stove's manual generally includes information about which types of flooring are safe.
Other things to consider regarding stove placement include the availability of outside air for combustion and the stove's proximity to a properly wired outlet. Access to clear venting, either horizontally through an outside wall or vertically through a ceiling and roof, is another requirement.