Realistic blood? I believe what you want is not realistic blood but rather art that pops. This is more of an art and animation question, but on the technical C2 side, for static bloodstain, you will probably need canvas plugin to have bloodstains all over the place without having actual blood sprites: plugin-canvas_t64239
For blood spill animation, you might want to read on some animation principles and look through how some games made bloodspill look good frame by frame and try imitate them. For example: http://www.spriters-resource.com/arcade ... eet/32529/ See how blood got splashed on Metal Slug?
Also, this is a good read for animation: http://www.gamasutra.com/view/news/1766 ... _games.php
While some games use simpler to do "red dot" particles for a visual eye candy, having many objects like that tend to drag your CPU down with it. If you can make eye catching animation like in Metal Slug, you will only need just 1 explosive animation sprite and not 100 or so red dots per bloody explosion. But again, this is up to you.
Also, it is possible to use 1 object to show 10 bloodstain or bloodsplash, for instance. This is more work on art side, but it will use less objects, make game smoother and trick player that there are so many objects when actually there are only few.