The Alexamenos Graffito is a piece of grafitti found in Rome near Palatine Hill that mockingly states: "Alex worships his God". I visited Palatine Hill last summer and didn't get to see this.
This is what is known as a "hostile witness". In other words, it was created by someone critical of Christianity at the time. It accurately represents the impression that unbelievers had of Christians.
This inscription debunks several JW falsehoods:
1. Jesus didn't die on a cross
2. Jesus wasn't though of as God until Constatine pushed it through
3. Believers had ultimate love for Jehovah, but not Jesus.
Notice the bleeding heart the inscriber attributed to believers. Like Christians today, believers are overwhelmed that Jesus would die for someone as pitiful and sin ridden as they are. JW's on the otherhand are hoping to get eternal-life like a person hopes to win the lottery. Most JW's are fairly certain that their good works will be enough to be saved. It's too bad they ignore scriptures like this one: "By the works of the Law shall no flesh be justified".
Anyway, this artifact predates the Megiddo Mosaic by around 30 years (AD 200), and is a strong witness that supports a widespread belief among Pre-Constatine Christians that Jesus was indeed God, the Creator of heaven and earth.
This supports the conclusion that the hightest Christology is the earliest Christology.