Delay and Reverb are often used for guitar to thicken up the sound. You can play with the settings of your reverb (or delay) to get a particular sound, some settings may make your guitarsound more midrangy, while others may add more brightness or add a bit of fullness to the overal sound.

What is possible for guitar is also possible for vocals. There are these moments when you think your voice sounds too thin, you can work with the EQ settings on your mixer, you may try even various microphones to see which one gives you the best sound. If you still feel there is something lacking why not add some extra reverb to your vocals. You may even use the pedals you use for guitar to add some reverb to your vocals. Here are a few pointers you may find helpful:

                     @ To create a natural sound do not add too much reverb.
                    
                     @ Work with the overal mix: Listen to the sound of guitar, bass and drums before you add any reverb. Your vocals need to ride over the mix smoothly. If you do it right you will not even notice the reverb, You will only notice it when you sing without having any of the other instruments playing. A lot of people make the mistake to add too much reverb (or delay) with the result it makes the mix sound unnatural. Of course, you can go this way if you want it as special effect, but try not to add to much reverb if you strive for a natural mix and voca lsound.

                     @  The amount of Feedback from your delay will thicken up the sound, the amount of Time for the delay will add brightness to the sound. Work with the settings to achieve a natural sound.

                      @  Different rooms may ask for different settings, be aware of this. Settings which work for rehearsal room may need some tweaking when you play in another room (or venue)

Happy experimenting.
Eddie