In the tint2 docs do a ctrl-f for ‘icon’ — does any of that look like it could be of any use to you? I am not sure I understand the issue but maybe this:
launcher_icon_theme = name_of_theme : (Optional) Uses the specified icon theme to display shortcut icons. Note that tint2 will detect and use the icon theme of your desktop if you have an XSETTINGS manager running (which you probably do), unless launcher_icon_theme_override = 1.
launcher_icon_theme_override = boolean (0 or 1) : Whether launcher_icon_theme overrides the value obtained from the XSETTINGS manager. (since 0.12)
If not try searching for ‘icon’ in the rest of the repo, issues etc.