Designer for website template changes

I need a designer who is familiar with working with responsive web site templates. We need to make changes to a chosen template, and modify the template but keeping the structure of the html the same. For example, we will provide other marketing materials, so you can modify color palette of template to meet other branding for the client. We will provide or ask you to find relevant images to use to replace stock. You'll customize menu items, change headers, tweak layout, while maintaining the structure of the template so it is still easy to use the html. This is for ongoing work. Looking for long term relationship. No agencies please, this is for individual collaborator. Looking for someone who can turn things around quickly, work smart, and has agency-calibre work quality. Hours per week will vary, approximately 5-20. Some weeks will be slow, other weeks more.