Documenting ideas, articles, primary sources, and images is the key to scholarship.
It's also the law.
More important, citing where you got your information is the ethical conduct of people in the arts. The Library provides reliable documentation that is traceable--that sets up a lineage of your ideas and information and protects you from disputes.
While it's always OK to use the free web for ideas and info--you don't want to end there. Use the library's research tools (databases), documentation guides (research guides and citation manuals) and resource services (librarians and IM Reference) to provide the "paper trail" to everything you use.
Use what you know about the work to go to the relevant tabs (above)
Do I know the artist's name?
Do I know the location of the work today?
Do I know the era of the work?
-> Scholarly histories of art (Pelican History, Oxford Art Online) BEGINNINGS
Do I know the subject matter?
-> Symbol Dictionaries; Books treating art by subject matter BOOK CATALOGS
Do I know the genre (outsider art, collage etc.)
-> Corpora [corpus]; Books addressing form of work SPECIALTY BOOKS