How can one tell this is a tiny spider? Something normal sized needs to be in the picture so the actual size of the spider can be known. It could be a huge tarantula just seeing it here with no other reference.
forgive me for being dense, but i'm not sure how this meets the challenge. it seems to be more of a macro shot than a miniature, but maybe that's my problem. the lighting is a little strong, and the shadow at the bottom is distracting. it might help to rotate the image so that the line from top to bottom is either parallel to the border, or more of a diagonal.
Does not meet the challenge. Compose and photograph something "miniature" in such a way that it conveys to the viewer that the subject of your photo is a tinier version of something that is normally larger.