If using outlines, don’t make them too heavy. This will prevent your artwork from sitting comfortably on the wall. Instead, use a more natural paintbrush stroke.
For a simple inkpen-style stroke, create a long thin circle (fill only), then drag it into your Brushes palette. Click New Art Brush, then click on the Stroke Options icon at the bottom of the palette and choose Hue Shift from the Colorization Method menu – this allows you to choose colours for this brush later. Select the Pen or Pencil tool and use your new brush for outlines.
To add depth and interest to your wall art, add textures to larger areas of flat colour. For the grass- style texture here, create the shape first, then draw pen lines where you want your texture to flow. Create the top and bottom lines, then use the Blend tool (Object > Blend) to create the in-between lines.
Create a solid circle and drag it into your Brushes palette again. Click New Pattern Brush, then Hue Shift in the Colorization Method menu. Apply this brush to your lines – you may need to make the lines into overlapping solid objects to fill spaces. You can adjust the brush size in the Brush Options menu. For easier colouring, select your new shapes and click Object > Expand Appearance, to make everything into grouped, solid shapes.