I'm in love with rotala colorata, rotala magenta & blood red, and ludwigia ovalis. All are easy to grow, don't need high tech to look nice, and like most stems can be trimmed any height you desire.
I second the tiger lotus too. They look stunning, and are very hardy and can be kept the size you want.
Alternatively, if frequent trimming isn't your favorite, colorful small to medium swords like ozelot, flame or purple knight are less maintenance. Vesuvius is smaller and green, but in a clump looks really cool and has been fairly undemanding for me.