I didn't say "rewards in heaven", but "rewards in the Kingdom" meaning the Kingdom on Earth.
Mat 5:19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.
Tattoos would be among the least of the commandments. It will not go well for anyone who breaks even the least of the commandments after becoming a believer. They will not lose their salvation, but they will lose honor and rewards.
Mat 16:27 For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works.
Rev 22:12 And, behold, I come quickly; and my reward is with me, to give every man according as his work shall be.
One example of such rewards is found in the Parable of Pounds (Luke 19:12-27). Another is that the disciples will receive a special reward as found in Mat 19:28. Mat 20:23 tells us that the reward of sitting on Yeshua's right and left hands will be granted to two individuals by the Father.