Image Quality Issues

I do not know why the image quality of my header and background look so bad.
Maybe it's just on my end. Does it look low resolution to anyone else? If so, any suggestions on how to correct this? The files I uploaded are higher than standard web quality. I believe they are 300 DPI.

Harry Potter - "Daydreams of Ginny"

I really like this in just black and white. I'm a little uncomfortable with Harry's shoes, they look awkward to me.
I want this to appear as if Harry is daydreaming of Ginny...I may need to work on that part a little more. 

Big Daddy ATTACKS!!!

Sketches for another Bioshock illustration. I'm having trouble with the splicer's hand. I plan to use the Little Sister from the second sketch in the final piece.

Shaun White

Quick sketch of the Flying Tomato. I do want to finish this at some point.

Mini Justice League sketches

I haven't posted here in awhile. Sorry. I do have a few projects I'm working on. Here are a few thumbnails in my series of mini Justice League characters. I hope to color these soon and will post the final pieces then.

Half-Life Ravenholm (Complete)

All done. I kinda cheated with the background but I really did not feel like redrawing all of that.

Half-Life Ravenholm (color progress)

Finally adding color. Almost done. Need to add values to Gordon and this part is done. I may add a background...not sure what I would use.