My only suggestion would to wat i do with any drawings.1st i'd look 4 pics of real blood splatter(hint google.ca or .com where ever u live i spos
)
2nd see how the blood acts, like see wat the common shapes are ex, sharp corners or smooth puddels.
3rd take in to concideration the situation, is some on being cut, or is a gun shot throw the back ? all these can change the look.
also when blood is met by air it tends to turn darker and more of a brown shade so if some one has a white shirt and they were stabed and were wondering about 4 awhile there shiry won't be a bright red.
well that's all i can think of. LATER
and good luck 
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