Hey man, you got some pretty good developement goin on in a bunch of places! Quads are really lookin good! Your improvement area is def. in your back. I was just recently helpin a friend of mine in the gym who wanted weak point help and had a generally good physique and he had the same problem.
I noticed you posted your deadlift at 455. I would suggest takin a good look at your deadlift form, from what I see in the gym, even guys that lift up good weight do so at the cost of sacraficing that deadlift form either with super wide stances or incorrect lift mechanics such as just muscling the weight up no matter what. Doin deads with extra attention to the form could really thicken up ur back and rear delts for a great all around look since you have great developement in other places!
If you think ur dead could use a lookin at my suggestion would be lose the belt if possible and grip straps. Pop ur rep range up to 15-20 reps, pick a weight thats tough to hit 15 reps with and then try to bring it to 20. Pickin a higher rep range should give you more leeway on practicin that form under tension, also if you start deadliftin high weights at high reps ur body is sure to be shocked and spark some growth in those areas.
Remeber during deads if ur roundn ur back just a bit ur sacraficin developement and safey. Keep that back correct and get a solid squeeze in ur back and delts in reps. After 20 good reps at a tough weight u shud huffn and puffn and ur back should be wrecked after a few sets. That kindof energy expenditure during those sets may even help shred u up on the way. Hope this helps, im sure theres tons of vids with deadlift forms around the site.
Finishin up the width, you could do some wide pullups or pulldowns, make sure ur using the lats as best u can!