On this design I mostly made very subtle changes. I've added a slight texture to the background using an art brush (chalk) and then expanding the result and dropping the opacity to blend it in nicely. The text for 'Invest' and 'Time' were also very slightly textured and curved a bit more using the simplify tool on a very subtle setting. The other improvement that was suggested was to add cufflinks to the the right hand with the LinkedIn logo on them. I decided not to do this in the end because I thought that it would clutter up the design and wouldn't add that much to the impact of the poster.
This poster had significant changes made to it after the presentation. I added a glow coming out of the laptop and a reflection on the man's glasses to make it clearer that it was a glowing screen in front of him. The screen was had a bit of perspective added to it so that it became more dynamic and matched the movement of the stripes in the background. The text was also adjusted appropriately. The main title text was also enlarged slightly and I put a line above and below it, this was to make it seem more filled out and to increase the impact of the poster. The stripes in the background were also changed so that they add more visual interest to the page with less relative detail to distract the viewer from the main message.
I also added a texture to the whole design to give it a grittier and a more appropriate look for the era its from. This was done in a different was to the first texture example. I used a paper texture from a high resolution .jpg file, imported it into Illustrator and Live Traced it. The opacity was also adjusted along with the blend mode. I personally think that although it took a lot longer, the end result was worth the experimentation.