I could not find any relevant information on this, but I find it hard to swallow that it\'s not doable.
How can I customise the arrow for the popovers? I already did
Twitter Bootstrap is based on Less.
If you want to change the appearance of its arrows use the bootstrap less variables to do so.
// Tooltips and popovers
// -------------------------
@tooltipColor: #fff;
@tooltipBackground: #000;
@tooltipArrowWidth: 5px;
@tooltipArrowColor: @tooltipBackground;
@popoverBackground: #fff;
@popoverArrowWidth: 10px;
@popoverArrowColor: #fff;
@popoverTitleBackground: darken(@popoverBackground, 3%);
// Special enhancement for popovers
@popoverArrowOuterWidth: @popoverArrowWidth + 1;
@popoverArrowOuterColor: rgba(0,0,0,.25);
If you are using Sass instead do the same with the Sass Variables.
Sadly the TB-Customizer doesn't have all the variables so you might have to compile it on your own.
Edit:
Good news the new Bootstrap 3 customizer now provides these options.