The pinging while spinning the wheel off the ground probably isn't the spokes. There's not enough change in anything when spinning in the air to cause pinging in spokes. If it's happening when spinning slowly, you're hearing small bits of debris playing Pa*****o as they bounce off nipples (or eyelets) as they move within the rim.

Debris in rims is common and of no concern. The confirmation that it's debris is to spin the wheel faster, which traps it in place against the rim's outer wall.

You probably will hear pinging when you mount the wheel and go for the first ride. That is the spokes settling, and will clear within a few minutes.