Yes, don't be afraid to include little memories and mentions about amusing quirks they may have had. Obviously nothing embarrassing, upsetting or disrespectful whatsoever - but just silly, harmless things that will make people who knew them smile and pause to remember the irreplaceable character whom they loved and whom they're now finally bidding farewell.
Did they never manage to make it down the high street in less than an hour, even when just going for a bottle of milk, as they'd always bump into a friend, acquaintance (or stranger!) and lose track of the time in chatting; did they have a mild obsession with Tipping Point and always have a carefully worked-out strategy that they eagerly shared as to whether they should have taken the trade or the money; did they have a strict personal rule that they never, ever wore blue on a Thursday?! etc. etc.
Of course, you want to hear all the facts about achievements about their life, but it's often the insignificant, silly stuff that makes people realise that it's OK to laugh out loud at something their loved one would have laughed along with, were they still here, even at a funeral.
I know it's a cliche, but it's absolutely true nevertheless: it's a celebration of a treasured person and their wonderful life, and all that they meant to you and enriched your life for the privilege of having known them; not an enforced non-stop glumfest.