Well, I've seen IANAL (I am not a lawyer) put in a message, so I write this with the IANAG (I am not a geologist) disclaimer.
Your continents look pretty neat. However, would any two of them easily fit together? From your numbered map, it appears that some might, but I would make the continental drift (actually former continental fit) more explicit. The fit does not have to be perfect (there are all those eons of erosion and earthquakes after all) but it should be roughly there. Its a bit hard to tell with some of your continents, you might want to think of streamlining and simplifying their shapes just a tad.
As for the plates themselves, other than making your world more realistic, why do you want to have them? If this world is a world for a roleplaying campaign or story you are writing, I wouldn't stress over the tectonic plates too much. Somehow I just can't see one of the Fellowship of the Ring saying "Ssh, we have to be careful, we're nearing a subduction zone"
That being said, If you are going to have the plates, streamline and alter the plate boundaries so it doesn't look like so much that you drew circles around your continents and left the remainder as huge "superplates".
Using the earth as a guide (http://www.physicalgeography.net/fun...als/10i_2.html), I would move some of the boundaries of your plates far out into the ocean (like the North American Plate is in the Atlantic). Also, don't be afraid to have plate boundaries right on the edge of your continents. Take a look at the eastern boundaries of the Pacific, Juan De Fuca, Cocos, and Nazca plates, they are right on the edge of North and South America (which may explain why you have such high mountains in those areas).
Another feature you've noted missing is volcanically formed islands on or near the plate boundaries. Try putting them near where you have 3 or 4 plates bumping into each other or two plates that due to the overall plate configuration are not able to slide past each other successfully or easily. Both areas tend to be volcanically active and remained "locked" enough that undersea volcanic activity over time is able to build up to the point of breaking the surface.
Also, try using the search feature with the term "tectonic plates" here on the guild. This subject has been covered before and you will find additional advice scattered in those old threads.
Good luck Laime and keep mapping.