It's very common for people to use images like that, but you may have invited selective enforcement by admitting you used somebody else's images. Others, who use images like that, aren't as honest as you, so they may escape enforcement for a while. But even on your own website, you may be subject to enforcement by your ISP, so that's no guarantee of safety, even where enforcement is lax or capricious, e.g. msn or yahoo.