"I will love you, until my dying day." (I took that from Moulin Rouge, one of my favorite films).
Other cute paragraphs I can think of are "You are my everything" my husband would say this to me frequently.
Or if you want to be really cute and personal, why not send him something that only the two of you will understand. Some sort of "inside" joke or use a nickname that you personally have for him..
The more you make it personal rather than generic or something that sounds like it's taken from a greeting card, the more effective it will be. At least that's what I think.
And don't be afraid to use humor when sending out a cute message to your boyfriend. Humor is the basis of all good relationships.
Forget about cute texts and paragraphs, guys only want one kind of text from their girlfriends... And as they say, a picture speaks a thousand words!
Before you text him though, make sure you trust him not to share it.
Make sure it's a flattering pose. If he does share it, then at least it's a pic you want people to see.
Don't go fully nude, it's always good to leave something to the imagination, it turns us guys on!