You can promote almost anything as long as it does not contain adult material. There is a "Acceptable Use Policy" located at the bottom of each page. I would encourage you to take a look at that. Here's an excerpt from the AUP:
Adult material is strictly prohibited on all IBO websites. Members may not advertise thirdparty adult websites, upload suggestive photos or videos, or use suggestive language on IBO websites. This goes for all aspects of the platform including but not limited to: Ads, PR's, Blogs, wall posts, comments, or videos. Any member posting adult material will be suspended from IBO without warning.