So, some of you may be aware of this already, it's a very useful site called Pinterest Trends.

https://trends.pinterest.com/

It defaults to trends in your own country, but you can change this. 

The initial page will show the latest trends, but this may be too broad, and you need to narrow it down to your niche.

So, click on the interests section. (Click on the image to see it better!)

If this still doesn't offer suggestions that are relevant to your website, scroll further on the left, and add a keyword. 

Here, you can see I have still picked a relatively broad keyword of Cheese, but it gives me lots of ideas.

Let's say I am interested in watermelon salad with feta cheese, as the weekly growth in search volume has increased by 200%.

Now, if I click on that, it gives me further data, and if I scroll further, it shows the most popular pins using that keyword.

That gives you an idea of what people are clicking on, and you can create your pins in the same style.

Here is my pin for this keyword.