There are lots of ways to "download pictures from your phone to your pc" so it's not clear what you are attempting and thus not really possible to tell why it's not working. It's also helpful to know what you have done with these pictures you received - saved them to your gallery?
If you're connecting in MTP mode (where the computer sees the phone as a media device and not a USB storage device - does LG not support the latter mode?), I find that really confusing and I'm guessing this is what you're doing. Personally to transfer files from my phone to my pc I tend not to use USB. I do one of three things depending on how big the files are, how many there are, and how lazy I am feeling. For a few pictures I'd probably email them to myself and open the email on my pc. For large transfers I use an app called "WebSharing Lite" which turns my phone into a mini webserver (connected to my home wifi) so I just navigate to
http://my.phones.ip:2112/ on my computer and point and click my way to happiness. And sometimes I might upload files to box or the like and go download them on the computer (rarely, but it's my wife's preferred method on her iphone). There are a bunch of other ways too