Librarians weren't trained in marketing or design. So we acquire these skills as we move through our experiences.
TIPS on flyer designs: google flyer images. Example: google image "author event flyer". Images will give you an idea on how to design a great looking flyer. Pick the one you are most drawn to because of the quick clarity of the message - that is to say, at a glance, it caught your eye, then notice why it caught your interest.
TIPS on free images: pixabay, creative commons, Harvard's pathfinder or google images / search tool / labeled for reuse. Recently, copyright has become an important issue because the County can be hunted for their deep pockets. The clipart was even removed from our office applications. Not to worry, we've found reliable online sources for cool images. Just get use to searching them.
Recently, we've created a marketing committee reeking havoc on our creative designs, limiting us to certain colors, fonts, and logo to support the branding efforts of the County. Due to the bureaucratic nature of the business, you do what you can, however, they should've hired an expert in design and marketing cause if your marketing ain't right, ain't no one gonna see it.
Some one donated a portable display board and I took it thinking it might be useful. It was stored for about a year and with a little bit of velcro, these display acrylics look great on the board in the lobby of the library. I love it!