Open iTerm.xcodeproj in Xcode. Compile the project and then copy the
iTerm.app file from ~/Library/Developer/Xcode/DerivedData/iTerm-XXX/Build/Products/Development.
The main part of this mod is that it has custom tab styles.
Go to Preferences > Appearance > Tabs.
Settings that I use:
# Tabs
Tab style: Aqua
Tab position: Bottom
[ ] Hide tab bar when there is only one tab
[x] Color tab labels on activity
[x] Hide tab number and tab close button
[x] Hide tab activity indicator
# Panes
[ ] Show per-pane title bar with split panes
# Window
[ ] Show border around window
[x] Hide scrollbar and resize control