More Infos on theVexels Lifetime Subscription Deal
Here's a nice little site I found that offers FREE daily clipart that you can use for print on demand (like Redbubble, Etsy, Teepublic, Merch by Amazon, etc.). They offer a free clipart set every 24 hours. After that, it goes on sale.
A common question about commercial license clipart: if you are uploading to Redbubble (or any third-party site): I strongly recommend that you MODIFY the artwork in some way to create an original piece of artwork. This helps avoid the potential for a copyright strike (because someone else could have uploaded the exact same design earlier).