The A-Z of Modern Design by 
Book Cover Designs by 
The Dictionary of Art by 
Encyclopedia of Clothing and Fashion by 
Encyclopedia of Comparative Iconography by Encyclopedia of World Art by 
Posters: A Global History by It is important to have a topic that is both manageable and researchable. Using keywords (important words from your research question) will help you focus. Since you may not know the terms frequently used by researchers and other experts in the field you are researching, collecting a pool of words based on your initial keywords will be of great use. You can find these new words by brainstorming. The below tools can help you do that.
Access thesauri by searching Google, Bing, DuckDuckGo or another search engine, Here are two common methods. Each keyword you are starting with is [your keyword] in these examples:
If you are having a hard time brainstorming, you may want to try one of these useful graphic dictionaries that help find synonyms.
Instead of searching using a browser as explained above, you can also go directly to your thesaurus of choice. Here are a few examples: