
Beefing up your axle and/or springs may be a moot point for you. From the looks of you cute little trailer, I'm guessing that it was built on a Harbor Freight frame and does not have brakes. In most states, if your trailer doesn't have brakes, it isn't supposed to weigh more than 1500 lbs, by law. I would just enjoy it for what it is and, when you're ready, sell it and upgrade.
Hmmm.... Looking at it again, the wheels do have 5 lug nuts; so, either the guy upgraded some already or it wasn't built on a HF trailer. Does it have brakes?