From the Model Mayhem FAQ:

How long does it take a new profile to be reviewed?
Once you submit your profile for review, it usually doesn’t take too long for a decision to come in. Until your profile is approved, it will not appear live on Model Mayhem.

Please note that occasionally it can take some time for your profile to be reviewed. Each profile is reviewed individually by several members before being approved, and occasionally there are thousands of profiles waiting to be reviewed.

If you have been waiting longer than 2 weeks for your profile to be reviewed, please contact the moderation team.