Static subject (e.g, buildings or landscape), bright sunshine, calm day, tripod, no difficult lighting or fancy 'arty' effects. Alamy just check for technical quality, not subject.
Doesn't this imply that images taken under other conditions -- cloudy, windy day, no tripod, difficult lighting, arty, etc. -- are unsafe? If so, isn't that a bit weird?
Safe is relative. Under other conditions it requires more technical skill to ensure that the image doesn't exhibit one of the faults that QC might fail it for. Why make life difficult for yourself in your first submissions? Alamy QC are not just evaluating the four photos, they are indirectly evaluating the photographer to find out if the photographer understands what is meant by technical quality and whether they have the equipment to achieve it and the skills and experience to use that equipment to achieve good results.
Don't worry, once your first 4 photos have passed you will have plenty of opportunities to submit more risky photos. However, I've found that I've become more critical of the quality of my submissions, and won't take the risk of submitting something that I know is marginal