I have installed a new theme, unchanged, so no BTH logos at the top. It is called vVide. There are several other standard themes there as well.
To install a different theme, click on 'PROFILE' 'ACCOUNT SETTINGS' From here choose Modify Profile, Look and Layout. Near the top of the page, it will say 'Current Theme' and the name of the theme, BTH2014. Click change next to that and choose the theme vVide.
This theme will work better on mobile phones.
Let me know how it goes, and if it works well, I will customise the theme a little bit.