When adding a new item, allow specification of more formats
Can you elaborate on what you're trying to do?
Here's a link to the documentation that lists the items that can be added to ArcGIS Online.
https://doc.arcgis.com/en/arcgis-online/reference/supported-items.htm
If your goal is to simply upload an image file and store it in ArcGIS Online, you can add any file on your device by dragging and dropping the file over the New Item dialog or clicking the option to upload from your device. You don't need to identify the file type beforehand. ArcGIS Online will identify it for you by its file extension, ask for clarification (e.g., what's in the ZIP file), or indicate file is not a supported type (e.g., 7z).
If your goal is to add image file for display as a layer in the map, then you need to add your image as an imagery layer. There are several ways to do that. Here's a link for more information.
https://doc.arcgis.com/en/arcgis-online/reference/map-image-elevation-imagery-layers.htm
Keep in mind that an if you want to publish an imagery layer and host it in ArcGIS Online, you'll need an ArcGIS Image for ArcGIS Online license.
Hope this helps,
Mike
@MikeMinami I know how to upload items, thank you. I'm just trying to upload a zip file containing a TIF-format raster, so that others can access and download it. But it's making me specify the item type when I do so, and the item type I have is not an option in the drop-down menu, so I have to tell it it's something that it's not, which is annoying.
As I wrote in the original post, "image collection" used to be an option but now that is gone. "Image file" is also not an option, even though it is in that list of "Items you add to ArcGIS Online" you referred me to.
As a matter of fact it's not accepting my upload at all, period, right now. So that's even worse than it being labelled as the wrong file type.
After some investigation, you are right. Image Collection has been removed as an option when adding a ZIP file in ArcGIS Online in the most recent update. This type typically serves as the source data for publishing an imagery layer in the Enterprise version. Publishing from an image collection isn't supported in Online.
However, the options to add a ZIP file of this type has exist previously, and customers like you used this type to store a collection of images not intended to be used to create an image layer. As a workaround, you can alternatly identify your zip file as "Photos with location" and NOT choose the option to also create a hosted feature layer.
Sorry for my confusion.
Mike