All of the options are great Rated 5 out of 5 stars
☻ If possible add an option to select an image instead of a symbol. And other option to custom background. And for text color? I need to combine with FF themes ☻Well... I'll try with some CSS code. Thanks for your fast answer ☻This review is for a previous version of the add-on (2.1.1-signed).
Link Status Redux is more easily portable (and also easier to implement ;-) because it doesn't have its own UI elements, but instead modifies the value of an already existing text element. Adding support for images would depart from this and thus be a lot of work, so I will not be doing it. However, if someone else manages to do it well, I would consider adding their patches to the code.
As for text and background color, those should follow the theme as only the text is changed. See the review "More customization (For Aides)" by Stef for hints on how to change color based on visited/bookmarked status.