Ugly desktop wallpaper help?

So i have been without desktop for about 2 months now i just let the light blue screen but i decided to put one and the problem is that its very ugly and with low pixels no matter what image size i pick it was not like this before when i went to google images i just picked large image 1024p - 740+ and it looked great now its ugly but the thing is its the same with smaller pictures its not ugly er its the same so my guess i have done something like putted some image pixel limit or some program that i installed i dunno if you can just help me i would it would be awesome