Graffiti is one of the few tools you have if you have almost nothing. And even if you don't come up with a picture to cure world poverty you can make someone smile while they're having a piss. - Banksy
Paint buildings. Have cool designs on man-hole covers (Japan already does this and was the inspiration for the 90's fad - Pogs). There's a lot of greys and browns a splash of colour would be a subtle way to improve everyones mood.
2. LED Lights
I hate them, they're far too bright when you're trying to sleep, but if they're kept away from houses they could brighten up paths. Imagine those strips you put at the back of your TV, but on the parchment. Wouldn't that be cool?
3. Photo Spots
What's the one thing we all do when we visit a new city? Take photos. What if we had photo spots around Cumbernauld? We've all been to malls where they have sections for taking photos (See Above.) What if you had sections throughout the town statues of flowers, streetlights, animals ect. People take photos looking great, share online and as a result the attitude towards the town goes up.
*You could also have music playing at these spots, drawing people in and boosting their mood before taking photos.
4. KTV/Laser Quest/Bowling ect.
We need more fun things to do with friends. We have bars (Even they're all closing down,) but if you don't want to drink options are really limited.
When I lived in China we'd go to KTV every week. You'd get a room to yourself where you could hang out with friends, drink dance and sing along to karaoke. Lots of people are too shy to sing infant of strangers, this way they only need to sing infant of friends.
There's tons more options - Mini Golf, arcade, axe throwing, go karting, escape rooms... you get the idea.
Get the animals back. It was always a fun wee trip to see them, now there's nothing. Maybe it costs too much to run, but it would be nice to see the return if possible.
Stick those jaggy spikes onto everyones roofs (check supermarkets) and before long they'll nest and terrorise another place.
7. Art Gallery
Showcase/sell local artwork. Galleries are always a fun way to spend your time.
8. Car Boot Sale
Have a monthly car boot sale. It builds a sense of community, allows people to make extra cash and allows you to pick up some hidden gems.