The one that caught my eye first was the "Meme generator". This was clearly created as an exercise in creating a new Visual. It shows that not all of the Visuals necessarily have to be "business ready", just fun or useful in some way. The "Meme Generator" is brilliant in its simplicity. All one can do with it is alter the text at top & bottom and choose the image that links to it.
As you can see to your left, I've tested the Meme Generator with an image of the famous "Steampunk Bacon Cat" embroidery from Urban Threads, a company that produces wildly awesome machine embroidery.
To obtain any of the custom visuals, visit the PowerBI Gallery of Custom Visuals, and click on the one that draws your interest. A dialog box with a description of the custom visual will pop up. The dialog box will also provide a download button and (at least in the case of the Meme Generator) a button to download a sample PowerBI file with examples of the custom visual in use.
After you've downloaded the "Meme Generator" custom visual and its sample file, double-click on the sample file to open it in PowerBI.
The "Meme Generator" custom visual sample file contains three examples of the Meme Generator in use. If you want to try creating your own Meme, click on the Cat icon (next to the "R" icon as seen below:)
This will create a "Meme template" for you, which conveniently has instructions for how to configure it.
In the Visualizations section, you will see the options for configuration.
Change the Top Text & Bottom Text to words appropriate to your Meme, then enter the URL of the image you wish to use for the meme. You may also add a title, change the background, or add a border. You can take a screen shot of the image - I used the "Send to OneNote" screen clipper to select the image then paste it into Paint so I can save it as an image ready to be posted.