I particularly love the image of Eilean Donan from above - I didn't get up there on my last trip but am inspired to try next time.
Sunrise and sunset - should we ever be lucky enough to see the sun again! - are brutal at this time of year (rising about 4.30 am and setting after 10 pm) so a few days of cloudy mornings/evenings are helpful to catch up on sleep. If you are not used to short nights an eyeshade can be useful for getting to sleep: if the weather is good it does not get truly dark in many places and not all hotel/B&B curtains are good at blocking light.
Make sure you bring or buy midge repellent - they are out and biting. My local forecast is "negligible" (1) on the Scottish Midge forecast (http://midgeforecast.co.uk/home/) and I have already been bitten while mowing the grass. I use Smidge, which seems to work when I remember to apply it, and it doesn't smell as bad as some other repellents. Some people recommend Avon Skin So Soft, but I hate the smell and it brings me out in a rash. Both are available at many outlets in Scotland. Even with repellent you will still get a a lot of midges around you, but they shouldn't bite. Some people use a midge net, but I find my glasses steam up and I cannot see anything on the camera if I use one. Don't underestimate the ability of the little critters to get up trouser legs and sleeves, into hair and down shirt collars! I was in Skye in September last year, when the forecast was only at level 2, and they were still what I would term "a [delete] nuisance" - it felt as though we were inhaling them they were so abundant. Apart form an effective repellent, your only hope at this time of year is a strong breeze. The Cairngorms should have fewer midges than Skye and the west.
If the weather is terrible and you are interested in folk history, I spent one very wet, low cloud day having fun photographing interiors at the Highland Folk Museum at Newtonmore - handy for the Cairngorms. They have buildings set up as they would have been at various points in the past. You get wet moving between the buildings, but can keep the camera dry.
Enjoy your trip - and I hope the weather improves!
