At about 7 months I started moving away from pureed foods (ie/ blended with the hand mixer) and instead just using a fork or potato masher and mashing foods, so they were a bit lumpier. I still stuck to fruit and veg, only adding bits of chicken mushed into a fruit or veg when DS was a week shy of 8 months.
Aside from the "regular" fruits and veg, DS ate:
Sweet potato mixed with peas and a spoonful of pureed leek went over really well. Sometimes a spoonful of orange juice added as well.
Dried apricots (sulphite-free, boiled til soft and pureed, mashing isnt' enough for these).
Blueberries and banana
Avocado and anything
Papaya
Parsnip and peas
Banana and plum
Instead of adding a lot of new foods, I just upped the amount he was getting. So at 6 months it may have been 1oz of apple, at 7 months it was 1oz apple and 1 oz pear, moving into the 3oz per meal, often 1 oz of three foods, sometimes just two foods but more of them.
If you can deal with mess, what I often did was put a spoonful or two of the mushy foods on DS's highchair tray and let him smear his hands in it, pick it up and squeeze it through his fingers and what not. It gave him something to do while I was feeding him. I've also always kept toys on his highchair tray (we have one sticky one with a suction cup that stands up and he can bat around), because I often find that it's not that he's done eating, just that he's bored of sitting still - eating isn't "fun" enough for him. Sometimes when he's really fussy and done with eating, I pick him up and sit him on my hip and offer him another bite - amazing that he'll often eat another 6 or 7 bites this way when he was as good as DONE while in his highchair.
I also think that at 7 months or so, weight gain slows down a bit. And, fruits and veg aren't really that calorie-laden, and are virtually fat free, so they won't really add any extra fat to him. If he's on the skinny side, it could be his nature, especially if you and your DH are lean. I also find that no one ever takes height into account when they weigh babies - my DS is on the 50th percentile for weight, but the 98th for height - so they oohhh and ahhhh about how his weight is "perfect" but you can guarantee that if he was on the 15th percentile for weight and the 50th for height they'd be telling me he's too thin!
We still haven't started finger foods - DS just will NOT take to them. Offer him a new plastic block he's never seen and he'll squeal and put it right in his mouth. Offer him a soft cooked carrot and looks as if I'm from another planet, takes it timidly from me and holds it to his mouth with a look of disgust before sucking on it for a second and tossing it on the floor.
