Pinterest is the place where I am bookmarking all kinds of ideas. I have also been exploring programming languages for design ideas. But I came upon this PDF of designs and realized that there are millions of public domain books online with lots of great graphics. This one is particularly helpful because it shows how to do a design manually rather than computer generated. Digitization of design to happen later through various steps.
Another style for those that don’t even want to use the computer for design work could be like a zentangle pattern where you would just use your material or tape as the canvas for your zentangle and let the laser do the rest.
That Zentangle stuff will be excellent when I have a large surface that I want to engrave something, but have no appropriate images/patterns in mind. Eventually even I have to admit celtic swirls aren’t supposed to be on every surface
I think it goes without saying that if you’re AT ALL interested in historical design that you should be aware of (and buying!) Dover Books. They publish works whose copyright has run out, plus lots of original material. They now sell design books that contain CDs of both raster and vector images from many periods in history, and they just recently introduced an online image resource, DoverPictura. They have phenomenal stuff to inspire you, and once you buy the books or images (oftentimes for very low prices) the images are yours to use in any way you want, including commercially.
Here is the first handful of books that came up on their site when I checked in:
I am working on a post for Islamic art. I have a fantastic book on the math, theology, design and art of Islamic patterns. That at least will give you another doodle to go for. And when all else fails Maori tattoo patterns.
There is a wide variety of stuff there (understatement) some only available low res, but lots of good high resolution scans if you look. Many are public domain, but the LOC does not enforce any kind of right authority, so you sometimes have to figure out the situation for yourself.