Ads can't appear sideways or upside down. Ads can't be segmented, contain multiple copies of itself within the ad, or appear to be more than one ad. Google also doesn't allow ads that expand beyond the frame or otherwise encroach on the app.
Note that in each image ad, we include a small informational graphic overlay. We will not resize your image to accommodate this element. Your ad should always be submitted in the full original format size and take this overlay element into account. If the ad you submit is resized in advance, there may be extra white space visible when your ad is displayed. You can preview how your ad will appear with this overlay during the ad creation process when creating a standard image ad or a template image ad in the Ad gallery.
AdMob developers have the option of using Smart Banners, which are ad units that will render screen-wide banner ads on any screen size across different devices in either orientation. Smart Banners help deal with increasing screen fragmentation across different devices by "smartly" detecting the width of the device in its current orientation, and making the ad view that size. When an image ad won't take up the entire allotted space for the banner, we'll center the image and use a hexagonal textile filler to fill up the remaining space. Note that AdSense backfill ads will be centered and have "transparent" filler. See the Google Developer guide for more information.
Relevance and quality
Image ads must be relevant to the advertised site or app. Ad images must be clear and recognizable, with legible text. We don't allow unclear, blurry, or unrecognizable images to be used in ads.
Strobing and flashing
Google doesn't allow strobing, flashing backgrounds, or otherwise distracting ads.
Mimicking app content, news articles, or text ads
Google doesn't allow ads that mimic publisher content or layout, or news articles and features. Ads may also not contain screenshots of Google Ads text ads or otherwise simulate a Google Ads text ad in any way.
Google assigns a family status to all ads to make sure that ads are shown to an appropriate audience. Image ads and the content they point to must be "family safe." Any image ads and their associated websites cannot contain "non-family" or "adult" content.