The TIF format is primarily intended for flattened images and is not generally used with the latest variation of that format which does support transparency. Omega, I'm sure does not support it because Omega is not an image editing application.
The first question is do you have Adobe Photoshop, Adobe Illustrator or CorelDRAW? The second question is about the image you are attempting to export out of Omega ... Is it a vector, an image or a hybrid? The third question is what application are you doing the brochure in?
If it is a vector, then export it out as an EPS and your background will not be present. If it is an image, it will require a vector and a masking of the vector to the image to eliminate the background and then an exporting of both in a format that supports masks. If you have Photoshop you can easily save the image in a format that supports transparency. Those format are Photoshop PSD, PNG, GIF and recently added TIF with transparency. If you don't have the ability to create a transparency supported format, then your only option would be to make the background in the brochure white, in which case everything gets easier.
I would recommend you look at what formats are supported by the application you are creating the brochure layout in and use the highest quality one. GIF as suggested by DrCas would be, IMO, a poor choice because the quality is the lowest of any of the formats that support transparency.
