Yes, it is okay for Christians to be cremated. There is nothing in the Bible that speaks against it. Normally, people from the Old and New Testaments were buried since cremation was not the custom. Plus, cremation can be difficult since it requires a large amount of heat and fire, so it's much easier to bury a person. Still, there are Biblical occurrences of people being burned.
- Joshua 7:25, “And Joshua said, ‘Why have you troubled us? The LORD will trouble you this day.’ And all Israel stoned them with stones; and they burned them with fire after they had stoned them with stones.”
- 1 Sam. 31:12, “all the valiant men rose and walked all night, and took the body of Saul and the bodies of his sons from the wall of Beth-shan, and they came to Jabesh, and burned them there.”
- 2 Kings 23:20, “And all the priests of the high places who were there he slaughtered on the altars and burned human bones on them; then he returned to Jerusalem.”
Ultimately, there is no difference between cremation and burying. When the body is buried, given enough time, it will completely disintegrate. So, cremation and burying ultimately lead to the same physical condition of complete disintegration.
In the resurrection, our infinitely powerful God who knows all things, will be able to produce our resurrected bodies. There is nothing to prevent God from accomplishing His promises to raise us.