Great News: APEX 20.2 is finally out and adds a Dropzone component. For me, it does not look as intuitive as the Plug-In did, so I tried to improve the UX of it with a few lines of CSS.
If you use sequences to generate primary key values make sure you use the checksum feature of APEX. Otherwise, users can easily discover data they should not be able to see by raising or lowering the numeric ID in the URL.
HTML 5 added a set of new HTML tags known as "semantic" tags to better structure websites. You should use them to avoid sinking in chaos with many levels of nested divs. They also have the benefit to make your website more accessible.
Tables make it hard to give hierarchy to data. To underline the importance of certain values in a table you can use chips that highlight the values with colors.
I want to share a little script I wrote which generates a DML scripts for blob values like images. The output script can be used in your schema install script with your other master data.