I want to bulk upload images to be used later. Is that default in Magento?
Yes there is, but it is for CMS content and not available to use for products and categories.
For products, you can certainly upload in bulk to the
media/import directory, and then use these images at a later date by running an import, referencing those files in the import file.
There are lots of extensions for galleries on Magento stores (for example this)