Ornithomimus has been studied for a number of years at this point. Therefore, a good amount of research comes up when it is searched for on the internet. The only problem I've had is finding quality links. This is the problem every week I believe, though, and we cannot force everyone online to have quality links on their pages sadly. Instead, I have one article I can link to and two good articles that can be found in the Journal of Vertebrate Paleontology if you have the ability to get into it through Taylor and Francis or BioOne.
The article that can be linked comes to us from McGill University's Rui Tahara of the Department of Biology. The 2009 thesis is about the cranial pneumaticity of Ornithomimus edmonticus. Cranial pneumaticity is a phrase which means that the skull has spaces in the bones for air to fill. Birds have skeletal pneumaticity in that their body is populated with air sacs within the different bones. Humans also have some pneumaticity in their skulls, where our sinus cavities are specifically. Tahara's 2009 thesis explores the evolution of cranial sinuses in Ornithomimus and how they are representative of birds cranial sinuses as well using CT scans and 3D reconstructions. The information is well outlined and detailed and it is clear that some thought and quality research have gone into the reconstructions presented. Overall, well worth reading.
The two articles found in the JVP are an updated and co-authored version of Tahara's thesis with his advisor Hans C.E. Larsson and a totally different article about new material found in Mongolia attributed to a derived ornithomimosaur. The Larsson/Tahara paper has the same title as above. The article on new material can be found here. I will attempt to read it today and have a summary drawn up this afternoon about that article. In looking just now I realized that this second article is open access at the moment, so if anyone reads it before I can get a chance to, please feel free to summarize along with me!