When I used pencil, oil pastel, marker, pen & color pencil to design an artwork relate to this kind of stuff before, it is a good result. It like Rock n roll, urban, entertainment, graffiti kind of feeling.
You can sketch some rock graffiti on other paper first based on something look like these https://www.google.com/search?client=tablet-android-samsung&tbm=isch&sa=1&ei=SNHCWtu8H8nlvAT0xI7oAw&q=graffiti+rock&oq=graffiti+roc&gs_l=mobile-gws-img.1.0.0l5.12575.14613..16360...0....1094.1522.1j1j1j7-1..........1..mobile-gws-wiz-img.......0i67.IFKQLivuacU%3D and have some hand-drawn sketches like these https://www.google.com/search?client=tablet-android-samsung&biw=600&bih=1024&tbm=isch&sa=1&ei=ANLCWqC_G4PwvgSU_KPgAw&q=rock+n+roll+graphic+design&oq=rock+n+roll+gra&gs_l=mobile-gws-img.1.4.0l5.3091.10471..12268...0....131.796.4j4..........1..mobile-gws-wiz-img.......41.UTMv%2FOlbh2Y%3D have some splash https://www.google.com/search?q=splash&client=tablet-android-samsung&prmd=ivmn&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjBjqmW9JzaAhVHNo8KHZktC5QQ_AUIESgB below the conner like vignette.
Firstly, Have an original back up. Secondly, and add some your designed graffiti and design using black color pencil as finalize, add oil pastel coloring the graffiti and design in empty Background or behind the man. Have some splash below the conner. Remember the face, portait remain clear.
You can have a proffessional rock star poster design result now. This is tips related to Designers, Graphic Design, Advertising Design, Multimedia Design, Digital and Traditional.
~ Another option is use Copic liner black pen, Copic makers or Pen & Makers.
~ Most proffessional result be the same as industry, is to use software to design.