This does not seem to be in the same style of your avatar at all. Your avatar uses simple shapes and large blobs of color, as well as a varied color ramp including pink lighting and nice blue shadows. your piece so far appears to be dark grey and light grey, with no definition aside from a little bit of scribbling, and nothing to indicate that it is a building? Also it appears to be cut off rather abruptly on the right side of the image. It lacks a clear light source, interesting colors, contrast and helpful scale information such as windows or lines for the floors of the building.
EDIT - also, I should point out that the majority of pieces posted here are less than 128x128 and have no problem conveying a satisfactory amount of information. Your avatar could easily be adapted to a 64x64 px image or smaller without sacrificing any required detail, and it could be done with 16 colors as well.