One of the advantages of longboard is that they tend to be wider than the average 8 x 32 inch new school decks that have dominated skateboarding for years. This is particularly true when you start making your own boards and can make the as wide as you want. The only problem is that grip tape comes in 9-inch widths, narrower than most longboards. This leave you two options. Either you put it down the middle, leaving the rails ungripped, or cut the grip tape lengthwise and do some stripes, reminiscent of stringer is old surfboards. Then again maybe you want something different, something like custom grip tape.
My first attempt at custom grip tape came almost by accident. I had built a hybrid freestyle longboard, but had screwed up on the routing. A piece of advice, if you ever use a router on your homemade deck, do not use steel bits. They don't cut well and have a tendency to burn and gouge the wood. The extra money you spend on carbide router bits is well worth it. Anyway, when making this board, I had gouged one of the rails pretty bad, so I wasn't real concerned with what it was going to look like. I slapped some varnish on, more to keep the moisture out than to make it look decent. I just wanted to get it together and see how it rode. When I went to this mostly new school skate shop near my work to get grip tape, I found that they didn't sell it by the foot. They only sold it in roughly new school deck size pieces, so I bought two figuring that I would think of something later.
So now, not only did I have grip tape that was too narrow for the deck, it was too short as well. The only saving grace was that I wanted to leave a 3-4 inch space in the middle of the board ungripped, so that my toe could pivot on tricks like walk the dog. Here's what I came up with. I cut both pieces of grip tape lengthwise off center. For the edge in the middle where the ungripped part would be, I cut jagged lines sort of like the readout of a heartbeat on an EEG machine. I put the grip tape on so that the lengthwise stripe was off center to the right on the front of the board and off center to the left on the back. The end result looked mare like a mechanical torture device than an EEG readout--still not a bad look, especially if it distracted you from where I screwed up the routing.
By the time I built my next board, I had invested in some better tools, including carbide router bits, and my next deck came out much better, so I decide to have another shot at custom grip tape. My first thought was to do something Art Deco. I love Art Deco. I figured that the simple streamline geometric designs would be perfect for grip tape. Plus, I could do something with mostly straight lines. Straight lines are a good thing when you're cutting grip tape. Curves are a bitch. I went to the library to see if I could find any designs to copy. No deal, but I did find a great book on Polynesian design. There were only about twenty pages worth of pictures, so I photocopied them all. I finally decided to do a Tiki god, and then adapt patterns taken directly from the book. The end result is shown.
When I did this the hardest part was cutting the nose, eyebrows, and mouth on the Tiki god. As I said, curves are a bitch. The rest of it was relatively easy, time consuming, but easy. It was simply a matter of drawing the design on the paper backing of the grip tape and cutting with a utility knife and a steel ruler. Again, mostly straight lines helps here. Try cutting curves in grip tape free hand with a utility knife and you'll see what I mean.
The main thing you need to keep in mind is that grip tape eats utility knife blades for breakfast. When it starts getting hard to cut, it's time to change the blade, and you'll be doing that often. For this I use a utility knife that has a blade that is divided into sections that you can break off as they get dull. Also bear in mind that what you draw on the back of the grip tape is going to appear as a mirror image on the board. In most cases this won't matter, but if you're doing lettering, you'll need to draw in reverse on the back or cut directly on the top of the grip tape.
Once the design is all cut, it's fairly simple to put it on the board. If necessary, you can draw faint guidelines in pencil to help get the pieces on straight. These can always be erased when you're done. The last step is to trim around the edges of the board. For this use the side of a screwdriver to burnish the grip tape to the edges of the board. Rub the shaft of the screwdriver over the grip tape, following the contour of the board. Keep going back and forth until you have worn away the rough part of the grip tape and can see a well defined line around the edge of the board. This does two things. First, I pushes the edge of the tape down so that it won't start peeling up when you're finished. Second, it makes it much easier to trim around the edges. Just make sure that you have a nice sharp blade when cutting around the edges. A poorly cut line in the middle of an intricate pattern will hardly be noticed, but a bad cut on the rail where you have the shape of the board to draw your eye to it will stick out like a sore thumb.
That's about all there is to it. Your only limits are your imagination and your hand's ability to make a utility knife do what you want it to. The possibilities are endless and don't forget that grip tape comes in other colors besides just black. Maybe you want to try a nice two tone or get as many colors as you can find and do your own masterpiece on the top of your board.