Cutting away backgrounds in three images and combining them.

I have combined three images of my work on the homepage of my website; the overall look is good but my Photoshop skills are not good enough to achieve the required finesse. As I am considering using the combined image in some printed advertising as well I would like the job to be done properly. The handrail image is of a maquette with a plain background so fairly straightforward, the stainless balls need the background removing and the base blending in and the tiger is the main headache with a lot of open areas and a background of grass, fields and railings in a similar colour to the tiger. The smallest of the three images is currently 1200 x 900 pix but as the other two are 3456 x 2304 and 4592 x 3056 pix respectively I will re-take the smaller image at a similar resolution to ensure the widest possible use of the resulting image.