Are you talking about things we can physically create at our desks or photography, textures etc. as well?

Depends on what the budget and deadline will allow.

I'm talking about creating or buying a texture, an addon, a style, stuff like that. Vector elements such as florals for examples..

QFT - also depends on the usage; is this something that you may want to re-use for other pieces?

^That too.

Budget and Deadline are a huge factor. If you have the time to do something yourself do it. It adds to your portfolio and is easier on your wallet.

I'll make them when I have to. If I can find something ready made and legal to use from online then all the better.

The last thing I made was a bookshelf for our eBookstore.

I've also created a textured leaf with waterdroplets for a book cover before. Simply because the stock imagery was a lot of money and client didn't want to pay. I created a texture he liked for a fraction of the price that he was happy to pay.

It's good to have skills for moments like those.

Sometimes it goes the other way around too, where you get an idea in your mind but can't find a resource that depicts it as you would want, and you simply have to create it from scratch.

I had a client that needed a flyer to announce/publicize their seminar on food recalls. I couldn't find an inexpensive enough image that communicated the idea of a product recall, but I found an image on Google that was perfect – it was a news photo of an empty supermarket shelf with a taped-on paper sign explaining the recall. Of course, I couldn't use that exact image because it would have been copyright infringement. So... I used it as inspiration and re-created the idea of the image, and customized it specifically for the client. It was simple enough to create the basis of the image in Illustrator and add some blurring and other details in Photoshop. Didn't look 100% photo-realistic, but it worked perfectly for what I/the client needed.

I have done both. When possible, I like to create from scratch (as I'm sure everyone else does). But, I have bought stuff as well. Right now I'm redesigning a web site for a local non-profit group. I'm doing it pro bono, so I bought a $20 web template that already had all the features they wanted and a layout they liked. It was easier and quicker for me to buy a template that I can customize that will work than to spend hours developing one from scratch. The end result is they get something they like, so how it comes about isn't a big deal.