Why I am unable to change the wallpaper on my LG phone?

Hey buddy, delete some unwanted document from your phone memory. Try to restoring your factory setting also and try checking the size of the image. Or again deleting some things, if this fails, or there is nothing on the phone anyway, you are more than likely going to have to reset the phone. If nothing is working then most likely it has been infected with virus. Take it to nearest LG service centre to get it virus cleaned or install your own antivirus solutions if you can. Nothing much can be an issue just try this and I am sure you will be able to fix it. Even I faced the similar problem and I found that there was virus. So, I installed antivirus and after that everything is working fine. Good luck.