In Season 2 of Prison Break Agent Mahone finds out that Michael's last plan is related to this tattoo which contains a picture of Jesus Christ in a Rose, by which he concludes that this is his mother's name. I am wondering why would Michael need a tattoo which leads to his mother's name which is not difficult to remember as a son.
Certainly Michael is unlikely to forget his mothers name, however Christina Rose is not actually about his mother, nor is it the only piece of information in the tattoo.
In the episode S02E20- Panama, we see the full tattoo is Jesus Christ in a Rose with the number 617 on the stem:
Christina Rose Schofield, his dead mother, was no doubt the reason he picked the name, however Christina Rose is actually the name of the boat in Panama Michael and Lincoln are going to escape aboard:
And the 617 on the stem is the combination to the padlock which is securing the boat:
Michael has an impressive mind, so chances are he did remember all this anyway (although he did look at the tattoo in the episode which could be interpreted as him needing to check it), but it's better to be safe than sorry.
Furthermore, he may simply have needed to fill up the space. The prison designs and parts of the plan will only take so much space, and to look authentic he'd want it to be even.