Randall asks, "In Revelation 7, is the 144,00 people being marked on their foreheads literal or figurative?"
The Apostle John talks about the mark of the beast in Revelation 13. John wrote this:
Also it causes all, both small and great, both rich and poor, both free and slave, to be marked on the right hand or the forehead, so that no one can buy or sell unless he has the mark, that is, the name of the beast or the number of its name. This calls for wisdom: let the one who has understanding calculate the number of the beast, for it is the number of a man, and his number is 666. (Revelation 13:16–18 ESV)
The word translated “mark" is charagma (caragma) and John’s audience would have immediately picked up on its significance.
In the Roman empire, slaves were sometimes branded by their owners to show that the slave was the property of that particular estate. Soldiers would often brand themselves with the name of their general, revealing their undying loyalty to his cause. On every commercial contract or document, the documents were stamped with the name and date of the emperor which declared that the commercial activity upheld the name and authority of the emperor.
John’s readers would have understood this immediately. The Antichrist is placing his mark on his servants. He is indicating that they belong to his estate. They are also loyally devoted to his cause and they do nothing without a desire to honor the name of their emperor.
The passage you refer to, which describes the 144,000 Jewish witnesses being "sealed ... on their foreheads" (Revelation 7:3) suggests that this seal is also a literal, visible mark. The word used in the Greek can refer to a literal or figurative mark. For example, in Matthew's Gospel, the same word seal is used to describe the seal the Roman guards placed on Jesus' tomb.
Based on the fact that the mark of the beast is a physical mark, and based on the fact that this seal is placed "on the foreheads," which is a visible part of the body, I think our best understanding of this passage is that the 144,000 witnesses are given a literal mark.