Look Keo 2 and Look Keo are Look's current/previous range and they are compatible with each other.
Look Delta are Look's earlier range. I'm afraid they are not compatible with Keo's or Keo 2's
SPD-SL are Shimano's version of road pedals. These aren't compatible with Look products, (neither therefore are Look products compatible with them).
Checking out Look's web site, you don't see Delta pedals on there any more, but if you look at the various Keo pedals, they are clearly a different shape to yours.
Doing a quick web search for Look Delta reveals many images, including some on this page (Exustar pedals which are compatible with Delta's - I haven't embedded the image here in case there are copyright issues). What do you think?
Note lastly that even within the "Look Delta" genre, you can buy different cleats. The difference between them is how much your foot is allowed to move whilst in the pedal (known as floating). Red cleats offer 9° float, whilst Black cleats are fixed (0°). The general rule is to go for the more flexible red cleats unless you have a reason to do otherwise. (This applies to spd-sl and keo also, in fact for spd-sl there are three options.)