I would like to find an extension that manages custom product labels using only CSS for shapes, colour, text.
All the extensions that I have checked use images (jpgs, etc) to create the background image.
After more research:
IWD - Yes, is an option
Amasty - No, it does have an option to edit label with css but an image must be uploaded to use a label.
Yes, you are right. Our Custom Stock Status supports only images. But they are quite customizable, and the admin can add more if he needs.
Anyway, good luck to you in searching the solution you're looking for!
You can take a look at this Magento 2 Product Label: helps store owners to capture their site visitor’s attention, which motivates them to make a purchase decision faster.
By using Magento 2 product label extension, you can use a wide range of pre-made labels such as bestsellers, new arrival, exclusive, etc, or customize product labels on your personal preferences to highlight your products. Products attached to those labels create a feeling of urgency and desire for online shoppers to buy, and hence your store conversion rate goes up.
Hope this information is helpful!