blow away the cobwebs = literally to get rid of the webs that spiders make, this idiom means to do something which makes your mind "cleaner" and fresher: "After sitting in the same chair for five hours, I wanted to go out for a walk to blow away the cobwebs."
like a breath of fresh air = someone or something who has new, fresh ideas or behaviour: "After working for the old boss for 20 years, the new boss seems like a breath of fresh air."
out with the old, in with the new = to change the old for the new: "We have a new CEO who wants to make his mark on the company. Out with the old, in with the new."
new blood = to have fresh people and ideas in an organisation: "In an effort to get new blood into our research department, we're having a recruitment drive."
shake things up (a shake up) = to change things a lot: "The government are having a shake up of their education policies."
give something a new lease of life = to renew something so that it lasts longer: "Those tablets have given our pet dog a new lease of life."
breathe new life into = to give new energy to something: "This sports club needs to increase its members to breathe new life into our finances."
get a fresh perspective = to get a different point of view: "Let's ask the sales department for their opinion. The can bring us a fresh perspective."
see things from a different angle = to consider something from a different point of view: "Let's try to see this problem from a different angle."
go back to square one = to have to start again because something didn't work: "Well, so much for trying! I suppose it's back to square one."
go back to the drawing board = to have to start again because something didn't work: "Unfortunately the plans didn't work out. We'll have to go back to the drawing board."
start with a clean sheet = to have another chance, perhaps because you have made serious mistakes: "He's paid for his mistakes, and now he can start with a clean sheet."
make a fresh start / make a clean break = to start something again: "Let's put the problems behind us and make a fresh start."
Some other expressions with change
a change is as good as a rest = it's often as refreshing to make a change than it is to have a break
a change for the better / worse = a change that results in either a better or a worse situation
a change of heart = when you change your mind on something: "I've had a change of heart. I think I'll stay in my present job, after all."
loose change / spare change = coins in your pocket: "Do you have any spare change for the parking meter?"
small change = money of little value: "I've got about 5 euros of small change in my pocket."