Submit what you can. The visa officer is looking to establish two things:
- That your relationship is genuine
- That your relationship wasn't entered in to for the purposes of gaining access to Canada.
The correspondence, proof of visits to one another, and photos that you are asked to provide are pieces of evidence to support your application to show that both of the above apply, but primarily the latter. The visa officer is looking to establish that your relationship followed a normal progression for your culture. What they are really looking for is something that shows up as being out of the ordinary. For example, if a Canadian and a European were to get married after only a week of knowing one another, it would raise suspicions. Or, in some cultures large age differences between spouses are an indicator that the relationship may only be for a visa.
Photos, visits, and correspondence can point the visa officer to the conclusion that the relationship isn't primarily for the purposes of a visa, but if such evidence doesn't exist (i.e. photos weren't taken, or you didn't visit one another for example), then it is incumbent on you to explain to the visa officer looking at your file why this doesn't exist. It doesn't have to be much, but just explain briefly that you didn't think to take photos on your visit or whatever the case may be.
Do provide (within the limits of the checklist on number of pages and photos) what you have, though. Your correspondence and visits over the years are strong pieces of evidence, especially if dating back to 2003. Photos since your wedding are also important because they can show that you're building forth on your married relationship and presenting yourself as a couple. The officer will also be looking that your relationship is continuing after marriage. The logical next step is that you will want to be together, hence the application to come to Canada.
It is then up to you to provide other evidence that you may have that satisfies the officer that the two points mentioned above apply. You could include letters from family and friends saying they met your spouse before you were married, and that you presented yourself as a couple to them for many years (if that's truly the case, of course). Anything you can think of to show your relationship and that you are a couple can be included. But don't go overboard. An officer can always ask for more if they deem it necessary. Send them too much, and it may look like you're trying too hard. They may end up disregarding much of it anyway, if the other evidence is strongly in your favour already.