In this paper we proposed the use of spatial relations as a way of improving annotation-based image retrieval. We analyzed different types of spatial relations and selected the most adequate ones for image retrieval. We developed an image comparison and retrieval method based on conceptual graphs, which incorporates spatial relations. Additionally, we proposed an alternative term-weighting scheme and explored the use of more than one sample image for retrieval using several late fusion techniques. Our methods were evaluated with a rich and complex image dataset, based on the 39 topics developed for the ImageCLEF 2008 photo retrieval task. Results show that: (i) incorporating spatial relations produces a significant increase in performance, (ii) the label weighting scheme we proposed obtains better results than other traditional schemes, and (iii) the combination of several sample images using late fusion produces an additional improvement in retrieval according to several metrics.