I've seen tons of thestral pictures, but not of people actually riding them! So... anyway, HUGE OoTP spoiler here, so do not read the rest of this if you havent read the 5th book! . . .
This is from the scene when the 6 of them are on thier way to the Ministry Of Magic to 'save' Sirius. The sun is setting(providing me with my best background ever!) and Luna is treating this all as a 'normal daytrip'
UPDATE: 10-04, redid the nose, am thinking of updating the background (it'll look the same, just less messy)