Just putting in a plug for this site: https://www.nli.ie/en/about-our-collections-introduction.aspx
Lots and lots of digital images!
Here is their own Introduction: The National Library’s holdings constitute the most comprehensive collection of Irish documentary material in the world and offer an invaluable representation of Ireland’s history and heritage. Material acquired through Legal Deposit, donations and purchases is subsequently processed for storage and access. Providing appropriate storage and care for all collections is a vital part of our work and ensures its preservation for future generations.
The National Library collections comprise a number of formats; to facilitate easy navigation of this section of the website, collections have been grouped into four categories: Printed, Manuscripts, Visual, Digital. See the Accessing Material section to find out how to consult these collections.