Since you were starting from scratch, you should've gone for a bold image change.
Literal
One [from-から] do [reason-んだから], boldly image-change do-[should-have-すればよかったのに].
一から ('from one, from scratch') is a set expression for starting over completely. イメチェン is an abbreviation of イメージチェンジ ('image change'). 大胆に ('boldly') and すればよかったのに ('should have done, but didn't') create a regretful suggestion about a missed opportunity. The んだから explains the reasoning behind the advice.