I use alpine and have set w3m as the HTML reader in my mailcap file. w3m also displays images in HTML. Alpine is able to display most HTML emails just fine, but when it fails, I simply press V (which shows different mime parts of the message) and Enter (by default the focus is on the 2nd part, which is text/html; Enter launches the default html browser, which is w3m that displays the message). This gives all the benefits of alpine, with the option to display html+images in the same terminal if I need to.