The colors usually looks better and brighter when printed at a professional print press, so yes.
Also check the point size of the text on the Business Cards, make sure they are not below 7 pt…...The Business Cards look awesome!!
Nice and modern change, easy to read text on my screen, congrats!! (Still do not like those big badges!!)
You can use images portraits from photodune.com, with a link back to the image, just remove the portrait in the final main file. You cannot use images of celebrities, hope that helps.
Typography has a lot of aspect to it unfortunately it is not just about pairing the right fonts, here is a great article about Creating Exciting And Unusual Visual Hierarchies in Typography http://www.smashingmagazine.com/2013/02/26/creating-visual-hierarchies-typography/
@ muntashir, Don’t compare your designs to the worst designs on graphicriver, instead compare them to the best designs. Unfortunately from what I see, you will need to improve your typography skills and overall graphic design skills, I would recommend studying some tutorials over at http://design.tutsplus.com/
All the best.
You can use the low resolution preview, most times that is enough.