From 動画 to リンク and 壁紙 to pictures?

動画 are uploaded as リンク if ファンポップ doesn't support embedding from that site. So, for example, ファンポップ supports embedding from Youtube, so YouTube 動画 are uploaded in the "Videos" section of a spot. ファンポップ doesn't support embedding from Megavideo, though, so any Megavideo video あなた try to アップロード to ファンポップ will automatically be 投稿されました as a link.

As for the images, I'm not sure. What may have happened is that the 壁紙 あなた tried to アップロード was too small (the pixel size was too small) to be considered a wallpaper, so it was automatically uploaded as a photo. I think the same thing happens if あなた try to アップロード a very small picture (e.g. 100x100) - it gets automatically 投稿されました as an icon. I'm not 100% sure of this though, so someone correct me if I'm wrong.

ETA: So I just checked - when あなた go to アップロード an image, there's a handy little info box on the side of the screen. There, it says,

"Any 壁紙 uploads smaller than 800x600 will be re-categorized as photos, and any 画像 200x200 and smaller will be automatically re-categorized as icons."

So most likely your 壁紙 was too small.