I'll just say that Concrete Angel is a very hard song to sing because Martina absolutely belts it the whole way through, so it's a *big* song that usually requires a pretty big voice.
Here are just some cute songs that I think do really well for performances.
"Ever Ever After" by Carrie Underwood
"There's More to Me Than You" by Jessica Andrews
"If You Only Knew" by Savannah Outen
"Get Back" by Demi Lovato
"When You Look Me in the Eyes" by Jonas Brothers (not upbeat but a gorgeous, gorgeous song, especially for those with voices that have a very pure sound)
"Crush" by Mandy Moore
"Two Stars" from Camp Rock
"New Strings" by Miranda Lambert
"Fearless" by Taylor Swift
"The Call" by Regina Spektor
"Best Days of Your Life" by Kellie Pickler
And some people think they are boring or whatever, but I am firm believer that Disney songs are great songs to sing. They have personality, they're cute as can be, they show off vocal talent, and everyone always enjoys. These are some that I've always enjoyed singing:
"Part of Your World" from The Little Mermaid
"God Help the Outcasts" from The Hunchback of Notre Dame
"Reflection" from Mulan
"True to Your Heart" from Mulan
"Poor Unfortunate Souls" from The Little Mermaid
"Just Around the Riverbend" from Pochontas
"Colors of the Wind" from Pocohontas
"When She Loved Me" from Toy Story 2
"I Won't Say (I'm In Love)" from Hercules