I don't know if we could call this a rule, but a have noticed people are more receptive to graphics that do not take up the whole screen. 900 is borderline.
550 to 600 wide seems a good compromise, landscape format. In today's internet, the tendency is to either mix text, add bold titles, or collage jpgs. People fly through the internet. Naturally, the exceptions prove the rule. If you screenshot a Band-in-a-Box interface, the bigger the better for the sake of ease of reading smaller fonts. Many people take MS Paint for granted. You can easily resize, make montages, and add any style or color of text, along with draw and paint options.
Yeah, I've messed around with it a little: https://www.webdirectory21.com/color/butterfly/index.htm


Link: www.soundcloud.com/ed_shaw (Feel Free to Use)
https://drooble.com/edward.shaw/hymn/index.htm
Biab for WIN 2020 -- Win 10 64bit -- Reaper/Audacity
Zoom R-16 -- Tascam DP-03-SD -- SoundTap -- Crescendo --