There was in an depth discussion here about this:
https://bitcointalk.org/index.php?topic=1930321.0TLDR: Have an electrician install 240v 30a NEMA twist lock. Get a 240v 24a PDU (~$30 from eBay) 5,760 max watts. Get 2x PDU extensions (12v 240v each) (~$15).
Each extension can do 2,880w max. Get PC power cord for PDU extension (~$1-3 each). So depending on how many watts your rigs are pulling, you can do 2-4 rigs per extension, 4-8 rigs per PDU.
Also note that 240v will be more efficient than 120v by about 2%.
Also, the picture you posted looks super unsafe. It looks like there is water leakage around the panel and loose cables. If you prefer not to have your house on fire, I would get an electrician to look at that and clean it up and a plumber to look at the leak.