If you want to paint a room in your house a solid colour without any special finish or design, you might be able to tackle this job on your own. However, if you want to try a painting technique to dress up the paint and the look of the room, note why it's best to leave these, and some other types of painting, to the pros and why it's good to avoid trying to do these on your own.
Ombre refers to a fading of a colour; for residential wall painting, this is usually achieved by using different shades of the same paint colour, then adding water and brushing the paints together as they dry. This can be a bit tricky to do, as improper brushing techniques can mean streaks and lines rather than a faded colour. You also want to ensure you choose the right variations in colour tone so the fading is gradual and not pronounced, which is why it's best left to a professional.
A linen or fabric look is created by running a dry brush with thick bristles over wet paint. This also takes a bit more skill than you may realize, as the paint needs to be somewhat thick so that the brush bristles can push against it and create that woven appearance. It might also be good to use a white colour under the topcoat; the brush will scrape away some of the dominant colour and allow the white to show through, which will help those "fabric" scratches look more pronounced. However, if you add too much white paint or apply the top coat too thickly, this can make the paint look messy and not like actual linen.
Using stencils is a good way to add a design or even stripes to your walls, but these can be trickier to work with than you realize. If you don't keep the stencil straight, then of course the design or stripe won't be straight. Using too much paint or pulling the stencil away before it dries can also allow that paint to drip behind the stencil, ruining the effect.
Dark to light
If you're painting a light colour over a dark colour, this is often best left to a professional. You may need a certain primer that will cover that dark colour, or a certain type of topcoat that is less likely to let that dark colour bleed through. Trying to cover the dark colour with several topcoats may not be the best choice and may only result in a muddy, unattractive paint colour.
In order to avoid botched walls, contact professional repainting services in your area and leave the painting to the pros.