First, sorry for the harsh and direct opinions, since I can make a comment on designing poster (I usually can't comment on things good enough to be called comment)
I remember what my prof said to me 1 week ago: KISS (keep it simple, stupid ;please! Don't get offended! He's telling me
So yeah, he's telling me to make all my design to be as simple as I can (and a simple thing usually have much more impact in a poster.)
Imagine this: how many people will take a time to see your poster? What is the main attraction of your poster (in here, please use JUST one object as the main attraction, either it's typography or a drawing, so to emphasize the effect of the attraction. Two or more main object will confuse the audience)? What is it that will attract the attention of people, even though just for a second?
Imagine yourself as the audience, when you walk down a road, or driving, will you be attracted to SEE (not read first) a poster? Because when you're attracted to see a poster, then you'll start reading it. But how many percent of those 'passing bys' will see the posters while they walk, or doing something?
Ask yourself these questions: Why, When, Where, What, Who, How?
I myself find a poster is interesting enough if they're something like a guerilla poster or marketing
though usually it's not using a poster as its media, but it can be used with a poster too. Just think differently and creatively.
And, uhm, just my opinion though. Your poster might be better if you erase the... uhhh... rose petals (?) and erase the woman and the skulls. Maybeeeee, just draw a crawling hand from the bottom, show the bones and veins so it'll show that the hand really
try to get a help, really try to get out of the darkness. Maybe with the red ribbon tying the hand to the darkness. The hand try to reach the light. Make the color of the hand to be just black and white, that could emphasize the red ribbon. Maybe, make the ribbon glowing? Or, well, out of the box, make the ribbon not
a ribbon, but a red chain that have the same shape with that HIV logo? (And these all will make your poster just not your poster anymore...) Well, just my opinion ^^
Hope I can help ^w^
(Sorry for too many reference pictures)