After accepting Christ, do you have to be baptized to get to the next level in heaven?
First, there is no mention of different levels in heaven in the Bible. There is some indication that what each person has in heaven may not be exactly the same. See: Are there degrees of rewards and punishment?
Second, the Bible doesn't mention acceptance as a condition of salvation, unless you are using "acceptance" as a synonym to belief. Belief is required to become a Christian. "Therefore I said to you that you will die in your sins; for if you do not believe that I am He, you will die in your sins" (John 8:24). However, belief is not the only requirement. "You see then that a man is justified by works, and not by faith only" (James 2:24). A belief that isn't accompanied by action isn't a belief sufficient to save a person.
The Bible also speaks of the need to change your attitude toward sin and to give up your sinful ways. "Truly, these times of ignorance God overlooked, but now commands all men everywhere to repent" (Acts 17:30).
You also need to be able to stand up for your belief. "Therefore whoever confesses Me before men, him I will also confess before My Father who is in heaven. But whoever denies Me before men, him I will also deny before My Father who is in heaven" (Matthew 10:32-33).
Baptism is also a requirement for salvation because it is the act that symbolizes the change in the person. "Or do you not know that as many of us as were baptized into Christ Jesus were baptized into His death? Therefore we were buried with Him through baptism into death, that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life. For if we have been united together in the likeness of His death, certainly we also shall be in the likeness of His resurrection, knowing this, that our old man was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin. For he who has died has been freed from sin" (Romans 6:3-7). The claim that one is saved without baptism is false. "Corresponding to that, baptism now saves you -- not the removal of dirt from the flesh, but an appeal to God for a good conscience -- through the resurrection of Jesus Christ" (I Peter 3:21).