Here's a list that might be helpful to you if you're having trouble describing the character you want. This is all optional, of course. But the more specific you are in your descriptions, the closer I'll get with the pic.
- Photos that look similar to your character, previously done artwork of your character, or even your own personal sketches. These are often very helpful.
Scene & Pose:
- Picture orientation: Letter or landscape?
- Composition: Portrait or whole body?
- Pose: Facing viewer, profile, or partly turned? Still or moving? Standing or sitting?
- Angle: Are we looking upwards at him/her? Or looking downwards?
- Scene: What is the character currently doing? Fighting, crying, sleeping, etc.
- Mood: What kind of feel do you want? Dark and moody? Bright and happy?
- Location: Where does this take place? Indoors? Outdoors? Forrest? Dessert?
- Time: Ancient past? Distant future? Day? Night?
- Lighting: Dramatic and contrasty? Bright and fun?
- Weather: Sunny, cloudy, stormy, snowy, etc.?
- Species: Is your character human? Elven? Alien? Other?
- Race: Is your character white? Black? Asian? Other?
- Gender: Male or female? Or, uh, other?
- Age: Young or old?
- Height: Tall or short?
- Build: Muscular? Chubby? Lanky? Athletic? Thin? Emaciated?
- Features: Hair color and length, bangs or no bangs, eye color, etc.
- General appearance: Beautiful? Hideous? Average?
- Unusual traits: Scars, tattoos, rings, glasses, other special marks, etc.
Emotional & Social Traits:
- Mood: Is he/she currently happy? Sad? Embarrassed? Angry?
- Personality: Calm, shy, proud, serious, bouncy, talkative, insane, evil, etc.?
- Social status: Outcast? Popular? Criminal? King? Beggar?
- Occupation: What's he or she study in school or do for a living?
- Time period: Medieval, Renaissance, Victorian, futuristic, etc.?
- Articles of clothing: Shirt, pants, skirt, armor, robes? Long or short sleeves?
- Fabric: Wool, chain mail, silk, fur?
- Neatness: Are they dressed impeccably for a ceremony? Or sloppily?
- Weapon: Sword, bow and arrow, staff, etc.?
- Accessories: Hats, capes, etc.
- Props: Any weird objects? Pets? Super powers?
- Other considerations: Are they dressed conservatively? Or wearing sexy clothes?