Beginning with the game's 1.5 update, "being a veteran Ascended means honor, respect, and awesome rewards," according to the informational blurb on RIFT's website. We'll leave the honor and respect bit to your fertile imaginations, but the awesome rewards are quite tangible. They include full Guardian and Defiant uniforms, personal vendors, and on-the-go mailboxes. You can also buy your way to full veteran status (and unlock the high tier rewards immediately) by purchasing a multi-month subscription.
Look for more details in our upcoming interview with Trion.
[Thanks to Ren54 for the tip!]