These thoughts/images are very common amongst us Aspies. However, in cases of OCD, the sufferer experiences thoughts/images that are against their will and which they find to be very disturbing. For example, a person afflicted with OCD might see a hammer and immediately gets thoughts about someone hammering and killing someone else. OCD thoughts are typically not as benign as the ones you described. There is a link between repetitive thoughts in Asperger's and repetitive thoughts in OCD. The difference is that OCD thoughts are typically not pleasurable, which is why OCD is classified as ego-dystonic, meaning that it is against the sufferers self-concept.
I experience both forms of thoughts. I might here a word or phrase and repeat it in my mind, regardless of the meaning of the word, but only if it sounds nice. This is a form of palilalia. The same goes for images. To my understanding, everyone, regardless of their neurological wiring, has experienced this, but, of course, for NTs it is not as frequent, so they generally do not become conscious of themselves doing it. I also have a formal diagnosis of OCD, and have suffered from severe intrusive thoughts during my late teens. Having intrusive thoughts caused me to consciously think of good thoughts or images to replace the horrible ones, but, as in most OCD cases, I found that it was close to impossible to get rid of the bad thoughts. That's where psychotherapy and medication came into play, and which has proved to be very helpful to me.