Here are some of my icons, facebook, friends, sociality, fMobi and lock screen.

I thought that the original fMobi icon was a bit too pixelated around the outside, so I made a new background for it and got the centre with the 'f' off the internet.

The lock screen icon has already been posted in this thread, but I thought I'd upload my version of it. There is now a keyhole in the middle and the padlock is transparent (I prefer this because I can now see my moving background through it).

You will have to rename the icons if you are going to replace the old ones, I just changed the file path of the icons in the .desktop files, that's why the names are different.