What colors are in his nursery?? I have all the faith in the world that you'll come up with the perfect idea for the little guy!! 18 month all ready huh? Wow, that's what baby Hailey is in now and she's 17 months. Keep us updated on what you decide. As a rule of thumb, I usually make crib size covers (sewn, quilted or crocheted) until they outgrow their cribs, then, if they are still the right size when youngin's move on to toddler beds which use a crib size mattress. That way they get more years of use.