Quoting lourenzo in comment #11 on #510304: Create Node Type for uploading images on install:

Although, we could detect if any node types have imagefields, and offer options on install so the user could set an existing node type as default repository for uploads.

Being able to choose the content type used for uploading images through imagefield_assist would be really helpful.

Many image gallery modules rely on using a particular content type for images; having two different image content types [when unnecessary] confuses users and complicates site administration.