I was thinking about building a 5-10 gallon for a planted betta tank and looking for interesting ideas for the tank and stand. Here are a couple I found:
Cmc3502's Saltwater Fish Tanks - Photo 3 - Full Version - Rate My Fish Tank -yes it is a 5 gallon!
Aquarium Stand 5 Gallon - by Randy @ LumberJocks.com ~ woodworking community

Has anyone built an interesting small tank, have one or seen pics of one?

With beta tanks, I like shopping around for interesting (large) glass vases. Mine are currently in one gallon cylanders, not quite as unusual as the ones you have pictured, but a lot less work also. (lol)

Vases are hard to hide a heater and filter in and I'd rather do 5 gallons. I might use a vase if I found just the right thing, any large vases I have seen were tall rather than wide though.

I saw a cool tank on ebay the other day, but cant find it now, but will keep hunting,

It was made out of a gum ball machine... he had put the filter in the bottom part. Picture of gum ball machine

I managed to find it on Ebay Picture of sweet machine fish tank. Here is the link for the tank on Ebay, where there are some other images, of where he has put pump etc Ebay Link

Thats cool, well not for a goldfish, but could work well for a betta.

Yeah I think its pretty cool, if I see anything else, I'll post them too.

I like the kind that look like LCD tvs that you hang on the wall... But they are kind of thin :/

How about making one yourself? Get some appropriate plexi glass from home depot or something and make it the shape you want. It can give you good practice for a larger tank some day lol

Aquatica Gallery 5 Gallon Honey Rose Fish Aquarium - eBay (item 190496014349 end time Feb-27-11 10:51:09 PST)

5 GALLON GLASS COFFEE TABLE AQUARIUM SET FISH TANK 24" - eBay (item 190429000394 end time Mar-06-11 20:49:50 PST)

you can always go to a place like Hobby Lobby and look in their Glass section and see if you can find something interesting there, they have all kinds of vases, bottles, jars. What would be cool would be like an old glass jar big enough to sit on the floor and put some filter mech. in there.

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Tank: 29g:guppies, balloon mollies, swordtail, 2 mollies
Hex: opaline gourami
10g 1F. betta

I've seen a few TV ones
How to Convert an Old TV Into a Fish Tank - wikiHow

Here are some more ideas, some are big one, but gives you ideas.

Link 1, Link 2, Link 3, Link 4, Link 5