Sorry, but it ain't up to you, especially if you have nothing in print yet.
99.9999999999997747839436% of the time, the publisher hires the illustrator, but on the bright side, if you sell your first manuscript to one of the really big houses, they'll pair you with a first-rate illustrator. Your own name might not be known but an illustrator with a following could tip the scale in your favor.
You probably won't have any input on the illustrations but that's standard operating procedure. Every publisher has a house style and every illustrator has an individual artistic vision. That means the author has to be the most willing to give, but it's worth it. You might not even see the illustrations until the publisher sends you the galleys.
It's the nature of the biz, and if you're willing to live with it and have a story worth publishing, you'll do just fine.
