I have never met an ad company that would let you use a bitmap file, or a tiff file, or any such format as your creative. They typically allow GIF and JPEG. S

I have never met an ad company that would let you use a bitmap file, or a tiff file, or any such format as your creative. They typically allow GIF and JPEG. Some do allow flash, but those are few and far between and even they heavily vet those who use Flash and require only established (and presumably honest) companies to do so. It really cuts down on the malicious usage. If someone is running 3rd party ads with unvetted systems, its probably because they are (a) ignorant of others (b) seduced by the high pay rates or (c) did something to get themselves blacklisted at more venerable agencies.