Well I don't have any stallions, or horses at all for that matter, but when I look at a stallions page, front and center should be pictures of him- conformation shots most important, then a shot of him in action. Pictures of any notable offspring would be most important, like if he sired a champion, then just conformation shots of his kids.
Make sure height is clearly stated. Any tests are also important, including color tests. Any major wins or acomplishments should be noted, as well as strong points in his conformation (Short back, amazing shoulder, etc.) Pedigree is also important, possibly with links to his sire/dam's page.