My own intention is to use a Raspberry Pi 3 Model B as a small desktop computer or a toy server. This might not be the actual or final use case, but this determines the kind of display I'm interested in. Something priced clearly below 200 € and clearly smaller than 15 inches.
In eBay, Amazon and such there are displays that are
- only panels with some control circuitry
- panels with an enclosure and a place for the Pi
- normal encased displays with connectors
- displays with some kind of touch functionality
- displays without any touch functionality
- display's maximum resolution is its physical resolution
- display advertises a large resolution and can accept it, but only has a meager physical resolution
- can be powered using any USB connection
- can be powered via USB 3 or USB C
- need a 12 V power source or a power brick
- are intended for monitoring, and have screw holes for a VESA 75 mount
- are intended for embedding, and lack compatibility with mounting hardware
There are Eyoyo displays for sale in both German and UK Amazon. Once one looks at the product description of any display, there is some confusion about resolutions and such. A 1280 x 800 display is suddenly 1024 x 800. Then there is a display with 1920 x 1280 resolution in the title, and in product details it's 1920 x 1200, but one is left guessing if it is 1920 x 1080 after all.
Then there are some 2560 x 1440 displays, which do mention Raspberry Pi in the product description, even though I wonder how is the maximum resolution going to work. One example is Ashata 13.3" which can be powered by USB if you have 2 A available.
Then there are Johnwill FHD monitors that are of the type that is suitable to be used as a secondary display with a laptop. But they do seem to also have the VESA 75 mount.
I could imagine some different use cases for the non-embedded purposes. Lots of these have to do with getting one display and then using it in a dual-purpose fashion with either Pi and a laptop or another computer or with Pi in different situations.
Use case one is a console for a home server. An USB-powered and HDMI-connected, smaller than 10".
Use case two is a laptop companion display, 10" to 15.6", FHD, USB powered.
Use case three is a plain standalone monitor, like an ordinary PC monitor, except smaller.
Decisions, decisions. All good decisions start with gathering enough information.