Welcome to the forum.
I don't see anything physically wrong inside the body...
Did you activate the sensor cleaning mode so that you could actually look at the sensor (with the mirror and shutter out of the way). The first thing I'd check, is if there is something physically on the surface of the sensor.
If there isn't anything there...then I'd agree, you're probably looking at a pooched sensor...and replacement cost for the sensor may be more than replacement cost for a used camera. Maybe it's a good excuse for an upgrade.