Battlefield 4 allows players to create their own custom emblem on Battlelog. The emblem in turn will then appear in-game on either a players weapons, occupied vehicle, or a player's screen who has been killed by the emblem's owner.
Now creating one of these can be a real pain, so here is an easy way to import some awesome emblems in only three step, requiring as little as Google Chrome
1: Head on over to emblemsbf.com and select one of the many emblems. Simply highlight the code and copy it (Control + C).
2: In a separate window/tab, navigate to Battlelog, sign in, and select “Customize Emblem” in the soldier section. Create a new emblem, and then hit Control + Shift + J in Google Chrome (Ctrl-Shift-K for Firefox, F12 in Internet Explorer), which will open up the console for the web page.customize-bf4-emblem
3: Go to the bottom of the console page, and paste the code (Control + V) that you copied from the emblem page. Hit Enter. Done
NOTE: Battlelog only allows up to Twenty Layers to be used for emblems, meaning that any Emblem exceeding that cannot be used. Premium members however, can utilize up to Forty layers.