How to make a wallpaper photo look good on the iphone?

I have an iphone 5 and today I was interested in changing my lock screen photo and homescreen. Both of the photos are the generic ones that the phone comes with. Anyway when I tried to put my own photos from the internet they looked very ugly, pixilated, and zoomed in to the point that the photos were unrecognizable. The last time I changed wall papers was on an iPod 4 gen and the pictures there looked perfect. No blurriness or anything else I mentioned. I figured it would be the same but clearly I'm doing something wrong. What's the trick, guys?

Be sure to download the picture after its fully loaded on the web.

And if neccisary use a cropping app to get the part of the picture you want.

Also, getting the right size of picture is huge. Make sure your typing in "phone wallpaper" after lets say "lamborghini… Phone wallpeper"