Improve or As Is?
The Uniform Residential Appraiser Report (URAR), which is published by U.S. mortgage lenders Fannie Mae and Freddie Mac, provides an overview of what home appraisers look for in preparing their reports. Going beyond or outside of this outline probably won't impact your home's value. Building inspection issues will have to be addressed separately, but "wish list" improvements or pet projects in addition to what is measured in inspections and appraisals likely won't be added into the value. Sometimes leaving areas "as is" is the best value for a home seller. In other words, if they're not broken, don't fix them.
If, after an appraisal, you decide not to sell for the appraised price and choose instead to make improvements with the hope of getting a higher sales price in the future, then you might want to reconsider whole house or room-to-room upgrades.