On the girders, I'd do something like this. (I have Photoshop, dunno the equivalents in PSP.)
Use the Magic Wand to select all the girder lines then rightclick and hit Layer via cut. Next, apply an outer glow to the layer and change the color to a dark grey and reduce the falloff distance. Then I'd make the space between the girder lines pure black. (Magic wand one then shift+click the reast to do them all at once.)
Flatten layers and it'll have a bit of a 3D-ish look. Might also try a little inner glow with the color and transparency set to look like shading. Or possibly bevel and emboss.
Whatever PSP has to add some texture to the girder parts should help them look less flat.