This is what I did if you want to put a picture that is the correct size from your computer onto your phone without using the verizon software.
What I did was basically, resize an image I liked to 960x800 using either photoshop or irfanview on my computer, then plugged my tbolt into my computer and chose the option of "mount as disk drive" in the options that come up, then a popup should come up on your computer giving you a few options on what to do with your phone. Close out of the one that has verizon on it, as there will be two popups. Now choose Open folder to view files which will let you see what's on your SD card. Then go to the folder named DCIM then the folder named 100MEDIA inside that. This is where all of your pictures will be. Drag the picture in there, go to your camera application and click the farthest left button to see your pictures. From there locate the picture, hit menu, then set as, wallpaper, then drag in the grey area to the left or right of the image to size it up all the way. Then click save and it will say cropping and there you go!
It sounds a lot more complicated than it is